RNA-dependent RNA polymerase (RdRP, RDR) or RNA replicase is an enzyme that catalyzes the replication of RNA from an RNA template. Four DNA polymerases wont be enough because each of these DNA polymerases that I recruited copied just approximately 3000 nucleotides, so that we need a huge number of DNA polymerases to proceed this way. Thus, eukaryotes contain multiple origins of replication distributed over the length of each chromosome to enable the duplication of each chromosome within the observed time of S-phase (Fig 2.9). [25] Pol ε is unique in that it has two zinc finger domains and an inactive copy of another family B polymerase in its C-terminal. Some viruses also encode special DNA polymerases, such as Hepatitis B virus DNA polymerase. This enzyme has one simple but crucial task: it catalyzes the attack of the 3’-OH from one fragment on the 5’ phosphate of the next fragment, generating a phosphodiester bond. In addition, an incorporation of a wrong nucleotide causes a retard in DNA polymerization. Because DNA is double stranded, each strand needs to be used as a template, but these strands are antiparallel. However, before the DNA polymerases take positions, they need to be primed. [41], Pol α (alpha), Pol δ (delta), and Pol ε (epsilon) are members of Family B Polymerases and are the main polymerases involved with nuclear DNA replication. [42] Due to its high processivity, Pol δ takes over the leading and lagging strand synthesis from Pol α. Chromosome replication begins with the binding of the DnaA initiator protein to an AT-rich 9-mer in OriC and melts (disrupts the hydrogen bonding between) the two strands. [7] DNA polymerase II was discovered by Thomas Kornberg (the son of Arthur Kornberg) and Malcolm E. Gefter in 1970 while further elucidating the role of Pol I in E. coli DNA replication. During the period of exponential DNA increase at 37 °C, the rate was 749 nucleotides per second.[15]. For this reason, they are said to work in a 5' to 3' direction. Once oriC has been opened and the helicases have attached to the two sides of the replication fork, the replication machine, aka the replisome can begin to form. DNA polymerase's ability to slide along the DNA template allows increased processivity. [32], DNA polymerase V (Pol V) is a Y-family DNA polymerase that is involved in SOS response and translesion synthesis DNA repair mechanisms. [14]:218–219 Pol δ is expressed by genes POLD1, creating the catalytic subunit, POLD2, POLD3, and POLD4 creating the other subunits that interact with Proliferating Cell Nuclear Antigen (PCNA), which is a DNA clamp that allows Pol δ to possess processivity. These polymerases have highly conserved regions that include two helix-hairpin-helix motifs that are imperative in the DNA-polymerase interactions. However, before the DNA polymerases take positions, they need to be primed. For an overview of the experiment, watch: Now, listen to the following story about these classic experiments by one of the scientists involved: Like many molecular events we will study, replication can be divided into three stages: initiation, elongation, and termination. Then we can … One motif is located in the 8 kDa domain that interacts with downstream DNA and one motif is located in the thumb domain that interacts with the primer strand. The last major player in the DNA replication story finally appears: DNA ligase. They are a riboprotein, as they are composed of both protein and RNA. What function does helicase perform during replication? Telomerases are RNA-directed DNA polymerases. [17] DP1, a Mre11-like exonuclease,[37] is likely the precursor of small subunit of Pol α and ε, providing proofreading capabilities now lost in Eukaryotes. [61][59], Bacteriophage (phage) T4 encodes a DNA polymerase that catalyzes DNA synthesis in a 5’ to 3’ direction. These enzymes catalyze the chemical reaction. [11] Pyrimidine:pyrimidine and purine:purine mismatches present less notable changes since the bases are displaced towards the major groove, and less steric hindrance is experienced. Stalled polymerases causes RecA to bind to the ssDNA, which causes the LexA protein to autodigest. They can only copy DNA in the direction that is opposite to the direction of DNA, which means that when we want to recruit four DNA polymerases, two of them, this one and this one, will be working just fine, but the two others won't be able to move because they cannot move in the same direction as the direction of DNA. E) None of the above. Note: the number of repeats, and thus the size of the telomere, is not set. Error correction is a property of some, but not all DNA polymerases. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. Recall that sister chromatids are identical copies of each other produced during S phase. Therefore, the new “strand” is not whole, but riddled with missing phosphodiester bonds. Members of Family Y have five common motifs to aid in binding the substrate and primer terminus and they all include the typical right hand thumb, palm and finger domains with added domains like little finger (LF), polymerase-associated domain (PAD), or wrist. They synthesize a primer that is then extended by DNA polymerases. The replication machine consists of the helicase, primases, and two DNA polymerase III holoenzymes moving in the same physical direction (following the helicase). The 5’-3’ exonuclease activity is crucial in removing the RNA primer. However, in larger, more complicated eukaryotes, with multiple linear chromosomes, more than one origin of replication is required per chromosome to duplicate the whole chromosome set in the 8-hours of S-phase of the cell cycle. The ... DNA replication is also a semi-conservative process where both strands of the double stranded DNA are used as templates for the DNA replication at the same time but in the opposite direction. [59] After infection, reverse transcription is accompanied by template switching between the two genome copies (copy choice recombination). These enzymes contain a small piece of RNA that serves as a portable and reusable template from which the complementary DNA is synthesized. 22. HeLa cells have been kept in culture since 1951. Cells lacking dinB gene have a higher rate of mutagenesis caused by DNA damaging agents. You can see that the resulting fragments, many fragments that are being built (called Okazaki fragments) complicate our life a little bit. This results in elongation of the newly forming strand in a 5'–3' direction. The loss of an interaction, which occurs at a mismatch, is said to trigger a shift in the balance, for the binding of the template-primer, from the polymerase, to the exonuclease domain. The 5’-3’ exonuclease binds to double- stranded DNA that has a single-stranded break in the phosphodiester backbone such as what happens after Okazaki fragments have been synthesized from one primer to the next, but cannot be connected. For example, the human diploid genome has 46 chromosomes (6 x 109 basepairs). Single-strand binding proteins bind to the single-stranded DNA near the replication fork to keep the fork open. 1968 Feb 10;243(3):627-38. An example of a retrovirus is HIV. This produces two new double-stranded molecules from one double helix. Pol III begins synthesizing by adding nucleotides onto the 3’ end of a primer and continues until it hits the 5’ end of the next primer. Figure \(\PageIndex{2}\): A PCR thermocycler system. In vitro single-molecule studies have shown that Pol III* has a high rate of RF turnover when in excess, but remains stably associated with replication forks when concentration is limiting. [29] Another single-molecule study showed that DnaB helicase activity and strand elongation can proceed with decoupled, stochastic kinetics. DNA polymerase cannot start synthesis de novo: DNA polymerases require a primer to initiate synthesis. The TERT subunit, an example of a reverse transcriptase, uses the RNA subunit to form the primer–template junction that allows telomerase to extend the 3' end of chromosome ends. These may selectively replicate viral DNA through a variety of mechanisms. It has been reported that the function of Pol ε is to extend the leading strand during replication,[44][45] while Pol δ primarily replicates the lagging strand; however, recent evidence suggested that Pol δ might have a role in replicating the leading strand of DNA as well. The presence of this zinc finger has implications in the origins of Eukaryota, which in this case is placed into the Asgard group with archaeal B3 polymerase. During SOS induction, Pol IV production is increased tenfold and one of the functions during this time is to interfere with Pol III holoenzyme processivity. How will the 3' end be replicated when there is no longer a place for a primer on the complementary strand? Bacterial replication (for example in E. coli) begins at... a single origin. The shape can be described as resembling a right hand with thumb, finger, and palm domains. DNA polymerases are a family of enzymes that carry out all forms of DNA replication. A complex of DNA polymerase and other enzymes that catalyzes the synthesis of DNA Involved in the simultaneous synthesis of both strands of DNA at the replication fork. General Features of Chromosomal Replication: … [59] From 5 to 14 recombination events per genome occur at each replication cycle. Lagging or Forward half strand (5' → 3') – DNA Polymerases work in stop-go fashion on Okazaki fragments [57], Plants use two Family A polymerases to copy both the mitochrondrial and plastid genomes. This reaction is believed to be catalyzed by a two-metal-ion mechanism. The proofreading exonuclease acts just like it does for Pol III, immediately removing a newly incorporated incorrect nucleotide. 2. DNA polymerases requires a free 3'-OH for it to synthesize the complementary strand, thus after the dsDNA is melted at its origin of replication it remains devoid of any complementary nucleotide sequence that can provide the DNA Pol with a free 3'-OH, this prevents the DNA Pol from carrying out its polymerization activity. For example, E. coli has a ~4.5 Mb genome (chromosome) that can be duplicated in ~40 minutes assuming a single origin, bi-directional replication, and a speed of ~1000 bases/second/fork for the polymerase. RNA polymerases can synthesize a DNA replication is called a semi-discontinuous process because while the leading strand is being synthesized continuously, the lagging strand is synthesized in fragments. Replication in eukaryotes starts at multiple origins of replication. [65], It was proposed that a mutational alteration in the phage DNA polymerase can stimulate template strand switching (copy choice recombination) during replication. As DNA polymerase proceeds along the template, the nucleotide that base pairs with each base on the template is covalently bonded to the 3 end of the growing strand. [29] In these studies, the replication fork turnover rate was about 10s for Pol III*, 47s for the ß2 sliding clamp, and 15m for the DnaB helicase. Pol α works by binding to the primase enzyme, forming a complex, where they both play a role in initiating replication. The DP1-DP2 interface resembles that of Eukaryotic Class B polymerase zinc finger and its small subunit. A number of possibilities have been proposed, but the current model is depicted here. Pfu belongs to family B3. [58], Retroviruses encode an unusual DNA polymerase called reverse transcriptase, which is an RNA-dependent DNA polymerase (RdDp) that synthesizes DNA from a template of RNA. [9], Each HIV retrovirus particle contains two RNA genomes, but, after an infection, each virus generates only one provirus. The polymerase activity then adds new DNA nucleotides to the upstream Okazaki fragment, filling in the gap created by the removal of the RNA primer. Pol κ is thought to act as an extender or an inserter of a specific base at certain DNA lesions. The gradual decrease in size of telomeres as the result of many replications over a lifetime are thought to be associated with the effects of aging. [23], Pfu DNA polymerase is a heat-stable enzyme of this family found in the hyperthermophilic archaeon Pyrococcus furiosus. They are more similar to bacterial Pol I than they are to mamallian Pol γ. [34] In E. coli, a polymerase “tool belt” model for switching pol III with pol IV at a stalled replication fork, where both polymerases bind simultaneously to the β-clamp, has been proposed. It is important to note that the directionality of the newly forming strand (the daughter strand) is opposite to the direction in which DNA polymerase moves along the template strand. DNA polymerase adds nucleotides to the three prime (3')-end of a DNA strand, one nucleotide at a time. LexA then loses its ability to repress the transcription of the umuDC operon. [21], Taq polymerase is a heat-stable enzyme of this family that lacks proofreading ability. Since DNA polymerase requires a free 3' OH group for initiation of synthesis, it can synthesize in only one direction by extending the 3' end of the preexisting nucleotide chain. Missed the LibreFest? The function of DNA polymerase is not quite perfect, with the enzyme making about one mistake for every billion base pairs copied. The 3' end of the … The accessory subunit binds DNA and is required for processivity of Pol γ. One example is the bypass of intra strand guanine thymine cross-link where it was shown on the basis of the difference in the mutational signatures of the two polymerases, that pol IV and pol V compete for TLS of the intra-strand crosslink. Fidelity is very important in DNA replication. J Biol Chem. However, although the different mismatches result in different steric properties, DNA polymerase is still able to detect and differentiate them so uniformly and maintain fidelity in DNA replication. [35], In 1998, the family D of DNA polymerase was discovered in Pyrococcus furiosus and Methanococcus jannaschii. Based on sequence homology, DNA polymerases can be further subdivided into seven different families: A, B, C, D, X, Y, and RT. Many DNA polymerases contain an exonuclease domain, which acts in detecting base pair mismatches and further performs in the removal of the incorrect nucleotide to be replaced by the correct one. What does the Replisome contain? Although the loss of such a small sequence would not be a problem, the continued rounds of replication would result in the continued loss of sequence from the chromosome end to a point were it would begin to loose essential gene sequences. There are a variety of different DNA polymerases with diverse sequences, and they have been … Asymmetry in DNA Replication Leading or Reverse half strand (3' → 5') – DNA Polymerase works non-stop – Completes replication sooner than the Forward half strand. DNA Polymerase I has three activities: (1) like Pol III, it can synthesize a DNA strand based on a DNA template, (2) also like Pol III, it is a 3’-5’ proofreading exonuclease, but unlike Pol III, (3) it is also a 5’-3’ exonuclease. This process corrects mistakes in newly synthesized DNA. Note that the energy is provided by the nucleotide triphosphate itself; two phosphates are released and one phosphate remains as a part of the phosphodiester bond. The rate of DNA synthesis in a living cell was first determined as the rate of phage T4 DNA elongation in phage infected E. coli. Following base excision, the polymerase can re-insert the correct base and replication can continue forwards. [10] The shape and the interactions accommodating the Watson and Crick base pair are what primarily contribute to the detection or error. Thus every molecule of DNA synthesis is actually initiated from a short (in E. coli, less than a dozen bases) RNA primer (these are depicted as short green lines in the figures above and below). DNA polymerase III binds to the strand at the site of the primer and begins adding new base pairs complementary to the strand during replication. Together Pol ζ and Rev1 add deoxycytidine and Pol ζ extends past the lesion. The reverse transcriptase family contain both DNA polymerase functionality and RNase H functionality, which degrades RNA base-paired to DNA. Unlike other DNA polymerases, the structure and mechanism of the DP2 catalytic core resemble that of multi-subunit RNA polymerases. In the case of DNA polymerase, the structure only allows it to add nucleotides to the 3' end of existing DNA, which presents some questions: 1. Core polymerase synthesizes DNA from the DNA template but it cannot initiate the synthesis alone or accurately. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Once it is bound, a nonprocessive DNA polymerase adds nucleotides at a rate of one nucleotide per second. In the absence of a primer, one must be provided de novo( pre-existing primers). But how are the new and old strands distributed? In 1956, Arthur Kornberg and colleagues discovered DNA polymerase I (Pol I), in Escherichia coli. Before replication can take place, an enzyme called helicase unwinds the DNA molecule from its tightly woven form, in the process breaking the hydrogen bonds between the nucleotide bases. The clamps are multiple protein subunits associated in the shape of a ring. [28] In-cell fluorescent microscopy has revealed that leading strand synthesis may not be completely continuous, and Pol III* (i.e., the holoenzyme α, ε, τ, δ and χ subunits without the ß2 sliding clamp) has a high frequency of dissociation from active RFs. DNA polymerases need RNA primers Start on DNA because they need existing templates DNA replication in Eukaryotes vs. Prokaryotes Histones tightly package DNA, which makes unwinding it harder to do in eukaryotes vs. prokaryotes Autonomously replicating sequences (ARSs) Occur ever 40-100kb Early-firing origins associated with active genes Later-firing origins associated with silent genes A and T bases … This leads to two major problems: first, there are little bits of RNA left behind in the newly made strands (just at the 5’ end for the leading strand, in many places for the lagging); and second, Pol III can only add free nucleotides to a fragment of single stranded DNA; it cannot connect another fragment. The first problem is resolved by DNA polymerase I. [64] A phage mutant with a temperature sensitive DNA polymerase, when grown at permissive temperatures, was observed to undergo recombination at frequencies that are about two-fold higher than that of wild-type phage. Purification and properties of deoxyribonucleic acid polymerase induced by infection with phage T4. [14]: Reverse transcriptase is commonly employed in amplification of RNA for research purposes. [17] Pyrococcus abyssi polD is more heat-stable and more accurate than Taq polymerase, but has not yet been commercialized. In order for the template strand that is 5’ to 3’ from left to right to be replicated, the strand must be fed into the polymerase backwards. Retroviruses encode an unusual DNA polymerase called reverse transcriptase, which is an RNA-dependent DNA polymerase (RdDp). Using the hydrolysis of ATP, a class of proteins known as the sliding clamp loading proteins open up the ring structure of the sliding DNA clamps allowing binding to and release from the DNA strand. DNA helicase, single-stranded binding protein, DNA polymerase III, DNA polymerase I, and DNA ligase. It does not (and can not) connect the strand it is synthesizing with the 5’ primer end. The sequence of amino acids in the C-terminus is what classifies Pol θ as Family A polymerase, although the error rate for Pol θ is more closely related to Family Y polymerases. The known DNA polymerases have highly conserved structure, which means that their overall catalytic subunits vary very little from species to species, independent of their domain structures. … In this way, genetic information is passed down from generation to generation. In prokaryotes, elongation proceeds bidirectionally until the replication forks meet. [35] However, the involvement of more than one TLS polymerase working in succession to bypass a lesion has not yet been shown in E. coli. [33] Transcription of Pol V via the umuDC genes is highly regulated to produce only Pol V when damaged DNA is present in the cell generating an SOS response. Most eukaryotes solve the problem of synthesizing this unreplicated DNA with a specialized DNA polymerase called telomerase, in combination with a regular polymerase. DNA replication in both prokaryotes and eukaryotes begins at an Origin of Replication (Ori). XXV. This preserves the integrity of the original DNA strand that is passed onto the daughter cells. The palm domain appears to function in catalyzing the transfer of phosphoryl groups in the phosphoryl transfer reaction. Different conformational changes and loss of interaction occur at different mismatches. Rev1 has three regions of interest in the BRCT domain, ubiquitin-binding domain, and C-terminal domain and has dCMP transferase ability, which adds deoxycytidine opposite lesions that would stall replicative polymerases Pol δ and Pol ε. This delay gives time for the DNA to be switched from the polymerase site to the exonuclease site. [52][53] Any mutation that leads to limited or non-functioning Pol γ has a significant effect on mtDNA and is the most common cause of autosomal inherited mitochondrial disorders. The main function of DNA polymerase is to synthesize DNA from deoxyribonucleotides, the building blocks of DNA. What do DNA polymerases require for replication to begin? DNA polymerases, which are multisubunit enzymes including Pol α, Pol δ, and Pol ε, are critical for the accurate replication of cellular DNA.277 While Pol α initiates DNA synthesis, Pol δ and Pol ε perform the majority of the DNA replication with Pol δ synthesizing the lagging strand and Pol ε synthesizing the leading strand. Because there are many repeats at the end, this fluctuation maintains a length buffer – sometimes it’s longer, sometimes it’s shorter – but the average length will be maintained over the generations of cell replication. The main role of Pol II is thought to be the ability to direct polymerase activity at the replication fork and helped stalled Pol III bypass terminal mismatches. This creates a checkpoint, stops replication, and allows time to repair DNA lesions via the appropriate repair pathway. The primer provides a site for the polymerization to begin. Thomas Kornberg, one of Arthur’s sons later found two more of DNA polymerases! So, in the single-stranded region trailing the helicase, if we look left to right, one template strand is 3’ to 5’ (in blue), while the other is 5’ to 3’ (in red). There are two pathways of damage repair leading researchers to conclude that the chosen pathway depends on which strand contains the damage, the leading or lagging strand. [14]:248–249, Pol γ (gamma), Pol θ (theta), and Pol ν (nu) are Family A polymerases. It fluctuates after each round of the cell cycle. How do cells resolve this problem? Pol II has 3'–5' exonuclease activity and participates in DNA repair, replication restart to bypass lesions, and its cell presence can jump from ~30-50 copies per cell to ~200–300 during SOS induction. As the Figure shows, the current model is that the primase is also moving along left to right, so it has just a short time to quickly synthesize a short primer before having to move forward with the replisome and starting up again, leaving intermittent primers in its wake. In E. coli, oriC is the site at which replication. As the DNA opens up, Y-shaped structures called replication forks are formed (Figure 1). Helicase and topoisomerase II are required to unwind DNA from a double-strand structure to a single-strand structure to facilitate replication of each strand consistent with the semiconservative model of DNA replication. Hydrogen bonds play a key role in base pair binding and interaction. The primary DNA polymerase for replication in E. coli is DNA Polymerase III (Pol III). During this process, DNA polymerase "reads" the existing DNA strands to create two new strands that match the existing ones. The reason why it does not work is that DNA polymerases are unidirectional. This increase is facilitated by the DNA polymerase's association with proteins known as the sliding DNA clamp. In a cell, DNA replication begins at specific locations, or origins of replication, in the genome. The DNA polymerases are enzymes that create DNA molecules by assembling nucleotides, the building blocks of DNA. [27] The third assembly is a seven-subunit (τ2γδδ′χψ) clamp loader complex. Prokaryotic family A polymerases include the DNA polymerase I (Pol I) enzyme, which is encoded by the polA gene and ubiquitous among prokaryotes. Mismatches in DNA base pairing can potentially result in dysfunctional proteins and could lead to cancer. [56] Pol ν (nu) is considered to be the least effective of the polymerase enzymes. Telomerase acts like other DNA polymerases by extending the 3' end, but, unlike other DNA polymerases, telomerase does not require a template. Polymerases in Family Y are low-fidelity polymerases, but have been proven to do more good than harm as mutations that affect the polymerase can cause various diseases, such as skin cancer and Xeroderma Pigmentosum Variant (XPS). During the synthesis of the new DNA molecule, where are the new nucleotides added by DNA polymerase? It polymerizes DNA from a template of RNA. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Explain why DNA ligase and not DNA polymerase is required to join Okazaki fragments. All DNA polymerases require a template strand, which is copied. The helicase will continue to travel in front of the fork to unwind new DNA and allow primase to add new primers as needed. DNA polymerases require the presence of a primer (i.e. The chi psi complex functions by increasing the affinity of tau and gamma for delta.delta' to a physiologically relevant range", "Single-Molecule DNA Polymerase Dynamics at a Bacterial Replisome in Live Cells", "Escherichia coli DinB inhibits replication fork progression without significantly inducing the SOS response", "Proficient and accurate bypass of persistent DNA lesions by DinB DNA polymerases", "A new model for SOS-induced mutagenesis: how RecA protein activates DNA polymerase V", "Managing DNA polymerases: coordinating DNA replication, DNA repair, and DNA recombination", "Genetic requirement for mutagenesis of the G[8,5-Me]T cross-link in Escherichia coli: DNA polymerases IV and V compete for error-prone bypass", "A novel DNA polymerase family found in Archaea", "Shared active site architecture between archaeal PolD and multi-subunit RNA polymerases revealed by X-ray crystallography", "DNA polymerases as useful reagents for biotechnology - the history of developmental research in the field", "The replication machinery of LUCA: common origin of DNA replication and transcription", "DNA polymerase family X: function, structure, and cellular roles", "Primary structure of the catalytic subunit of human DNA polymerase delta and chromosomal location of the gene", "Yeast DNA polymerase epsilon participates in leading-strand DNA replication", "DNA Polymerases Divide the Labor of Genome Replication", "A Major Role of DNA Polymerase δ in Replication of Both the Leading and Lagging DNA Strands", "Structural insights into eukaryotic DNA replication", "Saccharomyces cerevisiae DNA polymerase epsilon and polymerase sigma interact physically and functionally, suggesting a role for polymerase epsilon in sister chromatid cohesion", "Asgard archaea illuminate the origin of eukaryotic cellular complexity", "DNA polymerase zeta (pol zeta) in higher eukaryotes", "Phylogenetic analysis and evolutionary origins of DNA polymerase X-family members", "DNA polymerase β: A missing link of the base excision repair machinery in mammalian mitochondria", "Mitochondrial disorders of DNA polymerase γ dysfunction: from anatomic to molecular pathology diagnosis", "Mitochondrial DNA replication and disease: insights from DNA polymerase γ mutations", "Promiscuous DNA synthesis by human DNA polymerase θ", "Minireview: DNA replication in plant mitochondria", "Recombination is required for efficient HIV-1 replication and the maintenance of viral genome integrity", "The effect on recombination of mutational defects in the DNA-polymerase and deoxycytidylate hydroxymethylase of phage T4D", "Eukaryotic DNA polymerases: proposal for a revised nomenclature", Unusual repair mechanism in DNA polymerase lambda, A great animation of DNA Polymerase from WEHI at 1:45 minutes in, 3D macromolecular structures of DNA polymerase from the EM Data Bank(EMDB), UTP—glucose-1-phosphate uridylyltransferase, Galactose-1-phosphate uridylyltransferase, CDP-diacylglycerol—glycerol-3-phosphate 3-phosphatidyltransferase, CDP-diacylglycerol—serine O-phosphatidyltransferase, CDP-diacylglycerol—inositol 3-phosphatidyltransferase, CDP-diacylglycerol—choline O-phosphatidyltransferase, N-acetylglucosamine-1-phosphate transferase, serine/threonine-specific protein kinases, https://en.wikipedia.org/w/index.php?title=DNA_polymerase&oldid=995193426, CS1 maint: DOI inactive as of November 2020, Creative Commons Attribution-ShareAlike License, T7 DNA polymerase, Pol I, Pol γ, θ, and ν, Two exonuclease domains (3'-5' and 5'-3'), 3'-5 exonuclease (proofreading); viral ones use protein primer, template optional; 5' phosphatase (only Pol β); weak "hand" feature, This page was last edited on 19 December 2020, at 19:05.