1
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A transposon-derived DNA polymerase from Entamoeba histolytica displays intrinsic strand displacement, processivity and lesion bypass. PLoS One 2012; 7:e49964. [PMID: 23226232 PMCID: PMC3511435 DOI: 10.1371/journal.pone.0049964] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 10/15/2012] [Indexed: 02/06/2023] Open
Abstract
Entamoeba histolytica encodes four family B2 DNA polymerases that vary in amino acid length from 813 to 1279. These DNA polymerases contain a N-terminal domain with no homology to other proteins and a C-terminal domain with high amino acid identity to archetypical family B2 DNA polymerases. A phylogenetic analysis indicates that these family B2 DNA polymerases are grouped with DNA polymerases from transposable elements dubbed Polintons or Mavericks. In this work, we report the cloning and biochemical characterization of the smallest family B2 DNA polymerase from E. histolytica. To facilitate its characterization we subcloned its 660 amino acids C-terminal region that comprises the complete exonuclease and DNA polymerization domains, dubbed throughout this work as EhDNApolB2. We found that EhDNApolB2 displays remarkable strand displacement, processivity and efficiently bypasses the DNA lesions: 8-oxo guanosine and abasic site. Family B2 DNA polymerases from T. vaginalis, G. lambia and E. histolytica contain a Terminal Region Protein 2 (TPR2) motif twice the length of the TPR2 from φ29 DNA polymerase. Deletion studies demonstrate that as in φ29 DNA polymerase, the TPR2 motif of EhDNApolB2 is solely responsible of strand displacement and processivity. Interestingly the TPR2 of EhDNApolB2 is also responsible for efficient abasic site bypass. These data suggests that the 21 extra amino acids of the TPR2 motif may shape the active site of EhDNApolB2 to efficiently incorporate and extended opposite an abasic site. Herein we demonstrate that an open reading frame derived from Politons-Mavericks in parasitic protozoa encode a functional enzyme and our findings support the notion that the introduction of novel motifs in DNA polymerases can confer specialized properties to a conserved scaffold.
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2
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Selective modification of adenovirus replication can be achieved through rational mutagenesis of the adenovirus type 5 DNA polymerase. J Virol 2012; 86:10484-93. [PMID: 22811532 DOI: 10.1128/jvi.00739-12] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Mutations that reduce the efficiency of deoxynucleoside (dN) triphosphate (dNTP) substrate utilization by the HIV-1 DNA polymerase prevent viral replication in resting cells, which contain low dNTP concentrations, but not in rapidly dividing cells such as cancer cells, which contain high levels of dNTPs. We therefore tested whether mutations in regions of the adenovirus type 5 (Ad5) DNA polymerase that interact with the dNTP substrate or DNA template could alter virus replication. The majority of the mutations created, including conservative substitutions, were incompatible with virus replication. Five replication-competent mutants were recovered from 293 cells, but four of these mutants failed to replicate in A549 lung carcinoma cells and Wi38 normal lung cells. Purified polymerase proteins from these viruses exhibited only a 2- to 4-fold reduction in their dNTP utilization efficiency but nonetheless could not be rescued, even when intracellular dNTP concentrations were artificially raised by the addition of exogenous dNs to virus-infected A549 cells. The fifth mutation (I664V) reduced biochemical dNTP utilization by the viral polymerase by 2.5-fold. The corresponding virus replicated to wild-type levels in three different cancer cell lines but was significantly impaired in all normal cell lines in which it was tested. Efficient replication and virus-mediated cell killing were rescued by the addition of exogenous dNs to normal lung fibroblasts (MRC5 cells), confirming the dNTP-dependent nature of the polymerase defect. Collectively, these data provide proof-of-concept support for the notion that conditionally replicating, tumor-selective adenovirus vectors can be created by modifying the efficiency with which the viral DNA polymerase utilizes dNTP substrates.
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3
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Abstract
Viral polymerases play a central role in viral genome replication and transcription. Based on the genome type and the specific needs of particular virus, RNA-dependent RNA polymerase, RNA-dependent DNA polymerase, DNA-dependent RNA polymerase, and DNA-dependent RNA polymerases are found in various viruses. Viral polymerases are generally active as a single protein capable of carrying out multiple functions related to viral genome synthesis. Specifically, viral polymerases use variety of mechanisms to recognize initial binding sites, ensure processive elongation, terminate replication at the end of the genome, and also coordinate the chemical steps of nucleic acid synthesis with other enzymatic activities. This review focuses on different viral genome replication and transcription strategies, and the polymerase interactions with various viral proteins that are necessary to complete genome synthesis.
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Affiliation(s)
- Kyung H Choi
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.
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4
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Jurka J, Kapitonov VV, Kohany O, Jurka MV. Repetitive sequences in complex genomes: structure and evolution. Annu Rev Genomics Hum Genet 2007; 8:241-59. [PMID: 17506661 DOI: 10.1146/annurev.genom.8.080706.092416] [Citation(s) in RCA: 238] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Eukaryotic genomes contain vast amounts of repetitive DNA derived from transposable elements (TEs). Large-scale sequencing of these genomes has produced an unprecedented wealth of information about the origin, diversity, and genomic impact of what was once thought to be "junk DNA." This has also led to the identification of two new classes of DNA transposons, Helitrons and Polintons, as well as several new superfamilies and thousands of new families. TEs are evolutionary precursors of many genes, including RAG1, which plays a role in the vertebrate immune system. They are also the driving force in the evolution of epigenetic regulation and have a long-term impact on genomic stability and evolution. Remnants of TEs appear to be overrepresented in transcription regulatory modules and other regions conserved among distantly related species, which may have implications for our understanding of their impact on speciation.
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Affiliation(s)
- Jerzy Jurka
- Genetic Information Research Institute, Mountain View, California 94043, USA.
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5
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Berman AJ, Kamtekar S, Goodman JL, Lázaro JM, de Vega M, Blanco L, Salas M, Steitz TA. Structures of phi29 DNA polymerase complexed with substrate: the mechanism of translocation in B-family polymerases. EMBO J 2007; 26:3494-505. [PMID: 17611604 PMCID: PMC1933411 DOI: 10.1038/sj.emboj.7601780] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2007] [Accepted: 05/30/2007] [Indexed: 11/09/2022] Open
Abstract
Replicative DNA polymerases (DNAPs) move along template DNA in a processive manner. The structural basis of the mechanism of translocation has been better studied in the A-family of polymerases than in the B-family of replicative polymerases. To address this issue, we have determined the X-ray crystal structures of phi29 DNAP, a member of the protein-primed subgroup of the B-family of polymerases, complexed with primer-template DNA in the presence or absence of the incoming nucleoside triphosphate, the pre- and post-translocated states, respectively. Comparison of these structures reveals a mechanism of translocation that appears to be facilitated by the coordinated movement of two conserved tyrosine residues into the insertion site. This differs from the mechanism employed by the A-family polymerases, in which a conserved tyrosine moves into the templating and insertion sites during the translocation step. Polymerases from the two families also interact with downstream single-stranded template DNA in very different ways.
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Affiliation(s)
- Andrea J Berman
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Satwik Kamtekar
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Jessica L Goodman
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - José M Lázaro
- Centro de Biología Molecular ‘Severo Ochoa' (CSIC-UAM), Universidad Autónoma, Canto Blanco, Madrid, Spain
| | - Miguel de Vega
- Centro de Biología Molecular ‘Severo Ochoa' (CSIC-UAM), Universidad Autónoma, Canto Blanco, Madrid, Spain
| | - Luis Blanco
- Centro de Biología Molecular ‘Severo Ochoa' (CSIC-UAM), Universidad Autónoma, Canto Blanco, Madrid, Spain
| | - Margarita Salas
- Centro de Biología Molecular ‘Severo Ochoa' (CSIC-UAM), Universidad Autónoma, Canto Blanco, Madrid, Spain
| | - Thomas A Steitz
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
- Department of Chemistry, Yale University, New Haven, CT, USA
- Howard Hughes Medical Institute, Yale University, New Haven, CT, USA
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6
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Longás E, de Vega M, Lázaro JM, Salas M. Functional characterization of highly processive protein-primed DNA polymerases from phages Nf and GA-1, endowed with a potent strand displacement capacity. Nucleic Acids Res 2006; 34:6051-63. [PMID: 17071961 PMCID: PMC1635332 DOI: 10.1093/nar/gkl769] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
This paper shows that the protein-primed DNA polymerases encoded by bacteriophages Nf and GA-1, unlike other DNA polymerases, do not require unwinding or processivity factors for efficient synthesis of full-length terminal protein (TP)-DNA. Analysis of their polymerization activity shows that both DNA polymerases base their replication efficiency on a high processivity and on the capacity to couple polymerization to strand displacement. Both enzymes are endowed with a proofreading activity that acts coordinately with the polymerization one to edit polymerization errors. Additionally, Nf double-stranded DNA binding protein (DBP) greatly stimulated the in vitro formation of the TP-dAMP initiation complex by decreasing the Km value for dATP of the Nf DNA polymerase by >20-fold. Whereas Nf DNA polymerase, as the φ29 enzyme, is able to use its homologous TP as well as DNA as primer, GA-1 DNA polymerase appears to have evolved to use its corresponding TP as the only primer of DNA synthesis. Such exceptional behaviour is discussed in the light of the recently solved structure of the DNA polymerase/TP complex of the related bacteriophage φ29.
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Affiliation(s)
| | | | | | - Margarita Salas
- To whom correspondence should be addressed. Tel: +344 91 4978436; Fax: +34 91 4978490;
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7
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Truniger V, Bonnin A, Lázaro JM, de Vega M, Salas M. Involvement of the "linker" region between the exonuclease and polymerization domains of phi29 DNA polymerase in DNA and TP binding. Gene 2005; 348:89-99. [PMID: 15777661 DOI: 10.1016/j.gene.2004.12.041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2004] [Revised: 12/13/2004] [Accepted: 12/22/2004] [Indexed: 01/25/2023]
Abstract
For several DNA-dependent DNA polymerases it has been shown that their synthetic and degradative activities are organized in two separated modules. The functional coordination required between them to accomplish successfully the replication process is provided by important contacts with the substrate contributed by residues coming from both modules. These domains are connected by a central "linker" region adjacent to the "YxGG/A" motif, the putative limit of the polymerization domain. We describe here the mutational analysis of phi29 DNA polymerase in several residues of this region, connecting the N- and C-terminal domains and conserved in DNA polymerases able to start replication by protein-priming. The mutant polymerases with the less conservative changes showed reduced DNA binding activity. Additionally, their TP binding capacity was reduced, affecting the TP-deoxynucleotidylation in the absence of template. Interestingly, the role of the residues studied here in DNA binding seems to be especially important to start replication, when the polymerase enters from the closed binary into the ternary complex. These results allow us to propose that this interdomain region of phi29 DNA polymerase is playing an important role for substrate binding including both DNA and TP.
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Affiliation(s)
- Verónica Truniger
- Instituto de Biología Molecular "Eladio Viñuela" (CSIC), Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma, Canto Blanco, 28049 Madrid, Spain
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8
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Rodríguez I, Lázaro JM, Salas M, De Vega M. phi29 DNA polymerase-terminal protein interaction. Involvement of residues specifically conserved among protein-primed DNA polymerases. J Mol Biol 2004; 337:829-41. [PMID: 15033354 DOI: 10.1016/j.jmb.2004.02.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2003] [Revised: 02/04/2004] [Accepted: 02/06/2004] [Indexed: 10/26/2022]
Abstract
By multiple sequence alignments of DNA polymerases from the eukaryotic-type (family B) subgroup of protein-primed DNA polymerases we have identified five positively charged amino acids, specifically conserved, located N-terminally to the (S/T)Lx(2)h motif. Here, we have studied, by site-directed mutagenesis, the functional role of phi29 DNA polymerase residues Arg96, Lys110, Lys112, Arg113 and Lys114 in specific reactions dependent on a protein-priming event. Mutations introduced at residues Arg96, Arg113 and Lys114 and to a lower extent Lys110 and Lys112, showed a defective protein-primed initiation step. Analysis of the interaction with double-stranded DNA and terminal protein (TP) displayed by mutant derivatives R96A, K110A, K112A, R113A and K114A allows us to conclude that phi29 DNA polymerase residue Arg96 is an important DNA/TP-ligand residue, essential to form stable DNA polymerase/DNA(TP) complexes, while residues Lys110, Lys112 and Arg113 could be playing a role in establishing contacts with the TP-DNA template during the first step of DNA replication. The importance of residue Lys114 to make a functionally active DNA polymerase/TP complex is also discussed. These results, together with the high degree of conservation of those residues among protein-primed DNA polymerases, strongly suggest a functional role of those amino acids in establishing the appropriate interactions with DNA polymerase substrates, DNA and TP, to successfully accomplish the first steps of TP-DNA replication.
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Affiliation(s)
- Irene Rodríguez
- Instituto de Biología Molecular "Eladio Viñuela", Centro de Biología Molecular "Severo Ochoa", Universidad Autónoma, Canto Blanco, 28049 Madrid, Spain
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9
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Truniger V, Lázaro JM, Salas M. Two positively charged residues of phi29 DNA polymerase, conserved in protein-primed DNA polymerases, are involved in stabilisation of the incoming nucleotide. J Mol Biol 2004; 335:481-94. [PMID: 14672657 DOI: 10.1016/j.jmb.2003.10.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In DNA polymerases from families A and B in the closed conformation, several positively charged residues, located in pre-motif B and motif B, have been shown to interact with the phosphate groups of the incoming nucleotide at the polymerisation active site: the invariant Lys of motif B and the nearly invariant Lys of pre-motif B (family B) correspond to a His in family A DNA polymerases. In phi29 DNA polymerase, belonging to the family B DNA polymerases able to start replication by protein-priming, the corresponding residues, Lys383 and Lys371, have been shown to be dNTP-ligands. Since in several DNA polymerases a third residue has been involved in dNTP binding, we have addressed here the question if in the DNA polymerases of the protein-primed subfamily, and especially in phi29 DNA polymerase, there are more than these two residues involved in nucleotide binding. By site-directed mutagenesis in phi29 DNA polymerase the functional role of the remaining two conserved positively charged amino acid residues of pre-motif B and motif B (besides Lys371 and Lys383) has been studied. The results indicate that residue Lys379 of motif B is also involved in dNTP binding, possibly through interaction with the triphosphate moiety of the incoming nucleotide, since the affinity for nucleotides of mutant DNA polymerase K379T was reduced in DNA and TP-primed reactions. On the other hand, we propose that, when the terminal protein (TP) is present at the polymerisation active site, residue Lys366 of pre-motif B is involved in stabilising the incoming nucleotide in an appropriate position for efficient TP-deoxynucleotidylation. Although mutant DNA polymerase K366T showed a wild-type like phenotype in DNA-primed polymerisation in the presence of DNA as template, in TP-primed reactions as initiation and transition it was impaired, especially in the presence of the phi29 DBP, protein p6.
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Affiliation(s)
- Verónica Truniger
- Instituto de Biología Molecular Eladio Viñuela (CSIC), Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma de Madrid, Canto Blanco, 28049 Madrid, Spain
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10
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Truniger V, Lázaro JM, Salas M. Function of the C-terminus of phi29 DNA polymerase in DNA and terminal protein binding. Nucleic Acids Res 2004; 32:361-70. [PMID: 14729920 PMCID: PMC373294 DOI: 10.1093/nar/gkh184] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The thumb subdomain, located in various family B DNA polymerases in the C-terminal region, has been shown in their crystal structures to move upon binding of DNA, changing its conformation to nearly completely wrap around the DNA. It has therefore been involved in DNA binding. In agreement with this, partial proteolysis studies of phi29 DNA polymerase have shown that the accessibility of the cleavage sites located in their C-terminal region is reduced in the presence of DNA or terminal protein (TP), indicating that a conformational change occurs in this region upon substrate binding and suggesting that this region might be involved in DNA and TP binding. Therefore, we have studied the role of the C-terminus of phi29 DNA polymerase by deletion of the last 13 residues of this enzyme. This fragment includes a previously defined region conserved in family B DNA polymerases. The resulting DNA polymerase Delta13 was strongly affected in DNA binding, resulting in a distributive replication activity. Additionally, the capacity of the truncated polymerase to interact with TP was strongly reduced and its initiation activity was very low. On the other hand, its nucleotide binding affinity and its fidelity were not affected. We propose that the C-terminal 13 amino acids of phi29 DNA polymerase are involved in DNA binding and in a stable interaction with the initiator protein TP, playing an important role in the intrinsic processivity of this enzyme during polymerization.
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Affiliation(s)
- Verónica Truniger
- Instituto de Biología Molecular Eladio Viñuela, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Canto Blanco, 28049 Madrid, Spain
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11
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Gardner AF, Joyce CM, Jack WE. Comparative kinetics of nucleotide analog incorporation by vent DNA polymerase. J Biol Chem 2003; 279:11834-42. [PMID: 14699133 DOI: 10.1074/jbc.m308286200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Comparative kinetic and structural analyses of a variety of polymerases have revealed both common and divergent elements of nucleotide discrimination. Although the parameters for dNTP incorporation by the hyperthermophilic archaeal Family B Vent DNA polymerase are similar to those previously derived for Family A and B DNA polymerases, parameters for analog incorporation reveal alternative strategies for discrimination by this enzyme. Discrimination against ribonucleotides was characterized by a decrease in the affinity of NTP binding and a lower rate of phosphoryl transfer, whereas discrimination against ddNTPs was almost exclusively due to a slower rate of phosphodiester bond formation. Unlike Family A DNA polymerases, incorporation of 9-[(2-hydroxyethoxy)methyl]X triphosphates (where X is adenine, cytosine, guanine, or thymine; acyNTPs) by Vent DNA polymerase was enhanced over ddNTPs via a 50-fold increase in phosphoryl transfer rate. Furthermore, a mutant with increased propensity for nucleotide analog incorporation (Vent(A488L) DNA polymerase) had unaltered dNTP incorporation while displaying enhanced nucleotide analog binding affinity and rates of phosphoryl transfer. Based on kinetic data and available structural information from other DNA polymerases, we propose active site models for dNTP, ddNTP, and acyNTP selection by hyperthermophilic archaeal DNA polymerases to rationalize structural and functional differences between polymerases.
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12
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Dufour E, Rodríguez I, Lázaro JM, de Vega M, Salas M. A conserved insertion in protein-primed DNA polymerases is involved in primer terminus stabilisation. J Mol Biol 2003; 331:781-94. [PMID: 12909010 DOI: 10.1016/s0022-2836(03)00788-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein-primed DNA polymerases form a subgroup of the eukaryotic-type DNA polymerases family, also called family B or alpha-like. A multiple amino acid sequence alignment of this subgroup of DNA polymerases led to the identification of two insertions, TPR-1 and TPR-2, in the polymerisation domain. We showed previously that Asp332 of the TPR-1 insertion of phi29 DNA polymerase is involved in the correct orientation of the terminal protein (TP) for the initiation of replication. In this work, the functional role of two other conserved residues from TPR-1, Lys305 and Tyr315, has been analysed. The four mutant derivatives constructed, K305I, K305R, Y315A and Y315F, displayed a wild-type 3'-5' exonuclease activity on single-stranded DNA. However, when assayed on double-stranded DNA such activity was higher than that of the wild-type enzyme. This activity led to a reduced pol/exo ratio, suggesting a defect in stabilising the primer terminus at the polymerase active site. On the other hand, although mutant polymerases K305I and Y315A were able to couple processive DNA polymerisation to strand displacement, they were severely impaired in phi29 TP-DNA replication. The possible role of the TPR-1 insertion in the set of interactions with the nascent chain during the first steps of TP-DNA replication is discussed.
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Affiliation(s)
- Emmanuelle Dufour
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Instituto de Biología Molecular Eladio Viñuela (CSIC), Universidad Autónoma, Cantoblanco, 28049 Madrid, Spain
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13
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Abstract
Replication of the adenovirus genome is catalysed by adenovirus DNA polymerase in which the adenovirus preterminal protein acts as a protein primer. DNA polymerase and preterminal protein form a heterodimer which, in the presence of the cellular transcription factors NFI/CTFI and NFIII/Oct-1, binds to the origin of DNA replication. DNA replication is initiated by DNA polymerase mediated transfer of dCMP onto preterminal protein. Further DNA synthesis is catalysed by DNA polymerase in a strand displacement mechanism which also requires adenovirus DNA binding protein. Here, we discuss the role of individual proteins in this process as revealed by biochemical analysis, mutagenesis and molecular modelling.
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Affiliation(s)
- H Liu
- Centre for Biomolecular Science, Biomolecular Science Building, The University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, UK
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14
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Rodríguez I, Lázaro JM, Salas M, de Vega M. phi29 DNA polymerase residue Phe128 of the highly conserved (S/T)Lx(2)h motif is required for a stable and functional interaction with the terminal protein. J Mol Biol 2003; 325:85-97. [PMID: 12473453 DOI: 10.1016/s0022-2836(02)01130-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Bacteriophage phi29 encodes a DNA-dependent DNA polymerase belonging to the eukaryotic-type (family B) subgroup of DNA polymerases that use a protein as primer for initiation of DNA replication. By multiple sequence alignments of DNA polymerases from such a family, we have been able to identify two amino acid residues specifically conserved in the protein-priming subgroup of DNA polymerases, a phenylalanine contained in the (S/T)Lx(2)h motif, and a glutamate belonging to the Exo III motif. Here, we have studied the functional role of these residues in reactions that are specific for DNA polymerases that use a protein-primed DNA replication mechanism, by site-directed mutagenesis in the corresponding amino acid residues, Phe128 and Glu161 of phi29 DNA polymerase. Mutations introduced at residue Phe128 severely impaired the protein-primed replication capacity of the polymerase, being the interaction with the terminal protein (TP) moderately (mutant F128A) or severely (mutant F128Y) diminished. As a consequence, very few initiation products were obtained, and essentially no transition products were detected. Interestingly, phi29 DNA polymerase mutant F128Y showed a decreased binding affinity for short template DNA molecules. These results, together with the high degree of conservation of Phe128 residue among protein-primed DNA polymerases, suggest a functional role for this amino acid residue in making contacts with the TP during the first steps of genome replication and with DNA in the further replication steps.
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Affiliation(s)
- Irene Rodríguez
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Cantoblanco, E-28049 Madrid, Spain
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15
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Brenkman AB, Breure EC, van der Vliet PC. Molecular architecture of adenovirus DNA polymerase and location of the protein primer. J Virol 2002; 76:8200-7. [PMID: 12134025 PMCID: PMC155156 DOI: 10.1128/jvi.76.16.8200-8207.2002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2002] [Accepted: 05/13/2002] [Indexed: 11/20/2022] Open
Abstract
Adenovirus (Ad) DNA polymerase (pol) belongs to the distinct subclass of the polalpha family of DNA pols that employs the precursor terminal protein (pTP) as primer. Ad pol forms a stable heterodimer with this primer, and together, they bind specifically to the core origin in order to start replication. After initiation of Ad replication, the resulting pTP-trinucleotide intermediate jumps back and pTP starts to dissociate. Compared to free Ad pol, the pTP-pol complex shows reduced polymerase and exonuclease activities, but the reason for this is not understood. Furthermore, the interaction domains between these proteins have not been defined and the contribution of each protein to origin binding is unclear. To address these questions, we used oligonucleotides with a translocation block and show here that pTP binds at the entrance of the primer binding groove of Ad pol, thereby explaining the decreased synthetic activities of the pTP-pol complex and providing insight into how pTP primes Ad replication. Employing an exonuclease-deficient mutant polymerase, we further show that the polymerase and exonuclease active sites of Ad pol are spatially distinct and that the exonuclease activity of Ad pol is located at the N-terminal part of the protein. In addition, by probing the distances between both active sites and the surface of Ad pol, we show that Ad pol binds a DNA region of 14 to 15 nucleotides. Based on these results, a model for binding of the pTP-pol complex at the origin of replication is proposed.
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Affiliation(s)
- Arjan B Brenkman
- University Medical Centre, Department of Physiological Chemistry and Centre for Biomedical Genetics, Utrecht, The Netherlands
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16
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Truniger V, Lázaro JM, Esteban FJ, Blanco L, Salas M. A positively charged residue of phi29 DNA polymerase, highly conserved in DNA polymerases from families A and B, is involved in binding the incoming nucleotide. Nucleic Acids Res 2002; 30:1483-92. [PMID: 11917008 PMCID: PMC101840 DOI: 10.1093/nar/30.7.1483] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Alignment of the protein sequence of DNA-dependent DNA polymerases has allowed the definition of a new motif, lying adjacent to motif B in the direction of the N-terminus and therefore named pre-motif B. Both motifs are located in the fingers subdomain, shown to rotate towards the active site to form a dNTP-binding pocket in several DNA polymerases in which a closed ternary complex pol:DNA:dNTP has been solved. The functional significance of pre-motif B has been studied by site-directed mutagenesis of phi29 DNA polymerase. The affinity for nucleotides of phi29 DNA polymerase mutant residues Ile364 and Lys371 was strongly affected in DNA- and terminal protein-primed reactions. Additionally, mutations in Ile364 affected the DNA-binding capacity of phi29 DNA polymerase. The results suggest that Lys371 of phi29 DNA polymerase, highly conserved among families A and B, interacts with the phosphate groups of the incoming nucleotide. On the other hand, the role of residue Ile364 seems to be structural, being important for both DNA and dNTP binding. Pre-motif B must therefore play an important role in binding the incoming nucleotide. Interestingly, the roles of Lys371 and Ile364 were also shown to be important in reactions without template, suggesting that phi29 DNA polymerase can achieve the closed conformation in the absence of a DNA template.
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Affiliation(s)
- Verónica Truniger
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Canto Blanco, 28049 Madrid, Spain
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17
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Eisenbrandt R, Lázaro JM, Salas M, de Vega M. Phi29 DNA polymerase residues Tyr59, His61 and Phe69 of the highly conserved ExoII motif are essential for interaction with the terminal protein. Nucleic Acids Res 2002; 30:1379-86. [PMID: 11884636 PMCID: PMC101362 DOI: 10.1093/nar/30.6.1379] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2001] [Revised: 01/25/2002] [Accepted: 01/25/2002] [Indexed: 11/13/2022] Open
Abstract
Phage Phi29 encodes a DNA-dependent DNA polymerase belonging to the eukaryotic-type (family B) subgroup of DNA polymerases that use a protein as the primer for initiation of DNA synthesis. In one of the most important motifs present in the 3'-->5' exonucleolytic domain of proofreading DNA polymerases, the ExoII motif, Phi29 DNA polymerase contains three amino acid residues, Y59, H61 and F69, which are highly conserved among most proofreading DNA polymerases. These residues have recently been shown to be involved in proper stabilization of the primer terminus at the 3'-->5' exonuclease active site. Here we investigate by means of site-directed mutagenesis the role of these three residues in reactions that are specific for DNA polymerases utilizing a protein-primed DNA replication mechanism. Mutations introduced at residues Y59, H61 and F69 severely affected the protein-primed replication capacity of Phi29 DNA polymerase. For four of the mutants, namely Y59L, H61L, H61R and F69S, interaction with the terminal protein was affected, leading to few initiation and transition products. These findings, together with the specific conservation of Y59, H61 and F69 among DNA polymerases belonging to the protein-primed subgroup, strongly suggest a functional role of these amino acid residues in the DNA polymerase-terminal protein interaction.
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Affiliation(s)
- Ralf Eisenbrandt
- Centro de Biología Molecular Severo Ochoa (C.S.I.C.-U.A.M.), Facultad de Ciencias, Universidad Autónoma, Cantoblanco, E-28049 Madrid, Spain
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18
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Brenkman AB, Heideman MR, Truniger V, Salas M, van der Vliet PC. The (I/Y)XGG motif of adenovirus DNA polymerase affects template DNA binding and the transition from initiation to elongation. J Biol Chem 2001; 276:29846-53. [PMID: 11390396 DOI: 10.1074/jbc.m103159200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Adenovirus DNA polymerase (Ad pol) is a eukaryotic-type DNA polymerase involved in the catalysis of protein-primed initiation as well as DNA polymerization. The functional significance of the (I/Y)XGG motif, highly conserved among eukaryotic-type DNA polymerases, was analyzed in Ad pol by site-directed mutagenesis of four conserved amino acids. All mutant polymerases could bind primer-template DNA efficiently but were impaired in binding duplex DNA. Three mutant polymerases required higher nucleotide concentrations for effective polymerization and showed higher exonuclease activity on double-stranded DNA. These observations suggest a local destabilization of DNA substrate at the polymerase active site. In agreement with this, the mutant polymerases showed reduced initiation activity and increased K(m)(app) for the initiating nucleotide, dCMP. Interestingly, one mutant polymerase, while capable of elongating on the primer-template DNA, failed to elongate after protein priming. Further investigation of this mutant polymerase showed that polymerization activity decreased after each polymerization step and ceased completely after formation of the precursor terminal protein-trinucleotide (pTP-CAT) initiation intermediate. Our results suggest that residues in the conserved motif (I/Y)XGG in Ad pol are involved in binding the template strand in the polymerase active site and play an important role in the transition from initiation to elongation.
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Affiliation(s)
- A B Brenkman
- University Medical Center, Department of Physiological Chemistry and Center for Biomedical Genetics, Utrecht, The Netherlands
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19
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Abstract
Continuous research spanning more than three decades has made the Bacillus bacteriophage phi29 a paradigm for several molecular mechanisms of general biological processes, such as DNA replication, regulation of transcription, phage morphogenesis, and phage DNA packaging. The genome of bacteriophage phi29 consists of a linear double-stranded DNA (dsDNA), which has a terminal protein (TP) covalently linked to its 5' ends. Initiation of DNA replication, carried out by a protein-primed mechanism, has been studied in detail and is considered to be a model system for the protein-primed DNA replication that is also used by most other linear genomes with a TP linked to their DNA ends, such as other phages, linear plasmids, and adenoviruses. In addition to a continuing progress in unraveling the initiation of DNA replication mechanism and the role of various proteins involved in this process, major advances have been made during the last few years, especially in our understanding of transcription regulation, the head-tail connector protein, and DNA packaging. Recent progress in all these topics is reviewed. In addition to phi29, the genomes of several other Bacillus phages consist of a linear dsDNA with a TP molecule attached to their 5' ends. These phi29-like phages can be divided into three groups. The first group includes, in addition to phi29, phages PZA, phi15, and BS32. The second group comprises B103, Nf, and M2Y, and the third group contains GA-1 as its sole member. Whereas the DNA sequences of the complete genomes of phi29 (group I) and B103 (group II) are known, only parts of the genome of GA-1 (group III) were sequenced. We have determined the complete DNA sequence of the GA-1 genome, which allowed analysis of differences and homologies between the three groups of phi29-like phages, which is included in this review.
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Affiliation(s)
- W J Meijer
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma, Canto Blanco, 28049 Madrid, Spain
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20
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Dufour E, Méndez J, Lázaro JM, de Vega M, Blanco L, Salas M. An aspartic acid residue in TPR-1, a specific region of protein-priming DNA polymerases, is required for the functional interaction with primer terminal protein. J Mol Biol 2000; 304:289-300. [PMID: 11090274 DOI: 10.1006/jmbi.2000.4216] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A multiple sequence alignment of eukaryotic-type DNA polymerases led to the identification of two regions of amino acid residues that are only present in the group of DNA polymerases that make use of terminal proteins. (TPs) as primers to initiate DNA replication of linear genomes. These amino acid regions (named terminal region (TPR protein-1 and TPR-2) are inserted between the generally conserved motifs Dx(2)SLYP and Kx(3)NSxYG (TPR-1) and motifs Kx(3)NSxYG and YxDTDS (TPR-2) of the eukaryotic-type family of DNA polymerases. We carried out site-directed mutagenesis in two of the most conserved residues of phi29 DNA polymerase TPR-1 to study the possible role of this specific region. Two mutant DNA polymerases, in conserved residues AsP332 and Leu342, were purified and subjected to a detailed biochemical analysis of their enzymatic activities. Both mutant DNA polymerases were essentially normal when assayed for synthetic activities in DNA-primed reactions. However, mutant D332Y was drastically affected in phi29 TP-DNA replication as a consequence of a large reduction in the catalytic efficiency of the protein-primed reactions. The molecular basis of this defect is a non-functional interaction with TP that strongly reduces the activity of the DNA polymerase/TP heterodimer.
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Affiliation(s)
- E Dufour
- Centro de Biologia Molecular "Severo Ochoa", Universidad Autonoma, Cantoblanco, Madrid, 28049, Spain
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21
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Liu H, Naismith JH, Hay RT. Identification of conserved residues contributing to the activities of adenovirus DNA polymerase. J Virol 2000; 74:11681-9. [PMID: 11090167 PMCID: PMC112450 DOI: 10.1128/jvi.74.24.11681-11689.2000] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adenovirus codes for a DNA polymerase that is a member of the DNA polymerase alpha family and uses a protein primer for initiation of DNA synthesis. It contains motifs characteristic of a proofreading 3'-5'-exonuclease domain located in the N-terminal region and several polymerase motifs located in the C-terminal region. To determine the role of adenovirus DNA polymerase in DNA replication, 22 site-directed mutations were introduced into the conserved DNA polymerase motifs in the C-terminal region of adenovirus DNA polymerase and the mutant forms were expressed in insect cells using a baculovirus expression system. Each mutant enzyme was tested for DNA binding activity, the ability to interact with pTP, DNA polymerase catalytic activity, and the ability to participate in the initiation of adenovirus DNA replication. The mutant phenotypes identify functional domains within the adenovirus DNA polymerase and allow discrimination between the roles of conserved residues in the various activities carried out by the protein. Using the functional data in this study and the previously published structure of the bacteriophage RB69 DNA polymerase (J. Wang et al., Cell 89:1087-1099, 1997), it is possible to envisage how the conserved domains in the adenovirus DNA polymerase function.
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Affiliation(s)
- H Liu
- Centre for Biomolecular Science, The University of St. Andrews, North Haugh, St. Andrews KY16 9ST, United Kingdom
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22
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Böhlke K, Pisani FM, Vorgias CE, Frey B, Sobek H, Rossi M, Antranikian G. PCR performance of the B-type DNA polymerase from the thermophilic euryarchaeon Thermococcus aggregans improved by mutations in the Y-GG/A motif. Nucleic Acids Res 2000; 28:3910-7. [PMID: 11024170 PMCID: PMC110800 DOI: 10.1093/nar/28.20.3910] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The effect of mutations in the highly conserved Y-GG/A motif of B-type DNA polymerases was studied in the DNA polymerase from the hyperthermophilic euryarchaeon Thermococcus aggregans. This motif plays a critical role in the balance between the synthesis and degradation of the DNA chain. Five different mutations of the tyrosine at position 387 (Tyr387-->Phe, Tyr387-->Trp, Tyr387-->His, Tyr387-->Asn and Tyr387-->Ser) revealed that an aromatic ring system is crucial for the synthetic activity of the enzyme. Amino acids at this position lacking the ring system (Ser and Asn) led to a significant decrease in polymerase activity and to enhanced exonuclease activity, which resulted in improved enzyme fidelity. Exchange of tyrosine to phenylalanine, tryptophan or histidine led to phenotypes with wild-type-like fidelity but enhanced PCR performance that could be related to a higher velocity of polymerisation. With the help of a modelled structure of T.aggregans DNA polymerase, the biochemical data were interpreted proposing that the conformation of the flexible loop containing the Y-GG/A motif is an important factor for the equilibrium between DNA polymerisation and exonucleolysis.
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Affiliation(s)
- K Böhlke
- Institute of Technical Microbiology, Technical University Hamburg-Harburg, Denickestrabetae 15, 21073 Hamburg, Germany
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23
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Gonzalez-Huici V, Lázaro JM, Salas M, Hermoso JM. Specific recognition of parental terminal protein by DNA polymerase for initiation of protein-primed DNA replication. J Biol Chem 2000; 275:14678-83. [PMID: 10799555 DOI: 10.1074/jbc.m910058199] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The linear genome of Bacillus subtilis phage phi29 has a protein covalently linked to the 5' ends, called parental terminal protein (TP), and is replicated using a free TP as primer. The initiation of phage phi29 DNA replication requires the formation of a DNA polymerase/TP complex that recognizes the replication origins located at the genome ends. The DNA polymerase catalyzes the formation of the initiation complex TP-dAMP, and elongation proceeds coupled to strand displacement. The same mechanism is used by the related phage Nf. However, DNA polymerase and TP from phi29 do not initiate the replication of Nf TP-DNA. To address the question of the specificity of origin recognition, we took advantage of the initiation reaction enhancement in the presence of Mn(2+), allowing us to detect initiation activity in heterologous systems in which DNA polymerase, TP, and template TP-DNA are not from the same phage. Initiation was selectively stimulated when DNA polymerase and TP-DNA were from the same phage, strongly suggesting that specific recognition of origins is brought through an interaction between DNA polymerase and parental TP.
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Affiliation(s)
- V Gonzalez-Huici
- Centro de Biologia Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma, Canto Blanco, 28049 Madrid, Spain
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24
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Truniger V, Blanco L, Salas M. Analysis of O29 DNA polymerase by partial proteolysis: binding of terminal protein in the double-stranded DNA channel. J Mol Biol 2000; 295:441-53. [PMID: 10623537 DOI: 10.1006/jmbi.1999.3370] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
ø29 DNA polymerase, which belongs to the family of the eukaryotic type DNA polymerases, is able to use two kinds of primers to initiate DNA replication: DNA and terminal protein (TP). By partial proteolysis we have studied the regions of ø29 DNA polymerase involved in primer binding. With proteinase K, no change in the proteolytic pattern was observed upon DNA binding, suggesting that it does not induce a global conformational change in ø29 DNA polymerase. Conversely, two of the three main cleavage sites obtained by partial digestion of free ø29 DNA polymerase with endoproteinase LysC were protected upon DNA binding, indicating that the DNA could be occluding these cleavage sites to the protease either directly by itself and/or indirectly by induction of local conformational changes affecting their exposure. Partial proteolysis with endoproteinase LysC of ø29 DNA polymerase/TP heterodimer resulted in a protection and digestion pattern similar to that obtained with DNA, suggesting that both primers, DNA and TP, fit in the same double-stranded DNA-binding channel and protect the same regions of ø29 DNA polymerase.
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Affiliation(s)
- V Truniger
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma, Canto Blanco, Madrid, 28049, Spain
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