Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Saccharomyces cerevisiae RAD30 gene encodes a novel eukaryotic DNA polymerase, pol eta that is able to replicate across cis-syn cyclobutane pyrimidine dimers both accurately and efficiently. Very recently, a human homolog of RAD30 was identified, mutations in which result in the sunlight-sensitive, cancer-prone, Xeroderma pigmentosum variant group phenotype. We report here the cloning and localization of a second human homolog of RAD30. Interestingly, RAD30B is localized on chromosome 18q21.1 in a region that is often implicated in the etiology of many human cancers. The mouse homolog (Rad30b) is located on chromosome 18E2. The human RAD30B and mouse Rad30b mRNA transcripts, like many repair proteins, are highly expressed in the testis. In situ hybridization analysis indicates that expression of mouse Rad30b occurs predominantly in postmeiotic round spermatids. Database searches revealed genomic and EST sequences from other eukaryotes such as Aspergillus nidulans, Schizosaccharomyces pombe, Brugia malayi, Caenorhabditis elegans, Trypanosoma cruzi, Arabidopsis thaliana, and Drosophila melanogaster that also encode putative homologs of RAD30, thereby suggesting that Rad30-dependent translesion DNA synthesis is conserved within the eukaryotic kingdom.
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PMID:Novel human and mouse homologs of Saccharomyces cerevisiae DNA polymerase eta. 1045 7

The Saccharomyces cerevisiae RAD30 gene encodes DNA polymerase eta. Humans possess two Rad30 homologs. One (RAD30A/POLH) has previously been characterized and shown to be defective in humans with the Xeroderma pigmentosum variant phenotype. Here, we report experiments demonstrating that the second human homolog (RAD30B), also encodes a novel DNA polymerase that we designate poliota. poliota, is a distributive enzyme that is highly error-prone when replicating undamaged DNA. At template G or C, the average error frequency was approximately 1 x 10(-2). Our studies revealed, however, a striking asymmetry in misincorporation frequency at template A and T. For example, template A was replicated with the greatest accuracy, with misincorporation of G, A, or C occurring with a frequency of approximately 1 x 10(-4) to 2 x 10(-4). In dramatic contrast, most errors occurred at template T, where the misincorporation of G was, in fact, favored approximately 3:1 over the correct nucleotide, A, and misincorporation of T occurred at a frequency of approximately 6.7 x 10(-1). These findings demonstrate that poliota is one of the most error-prone eukaryotic polymerases reported to date and exhibits an unusual misincorporation spectrum in vitro.
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PMID:poliota, a remarkably error-prone human DNA polymerase. 1088 58

DNA polymerase activity is essential for replication, recombination, repair, and mutagenesis. All DNA polymerases studied so far from any biological source synthesize DNA by the Watson-Crick base-pairing rule, incorporating A, G, C, and T opposite the templates T, C, G, and A, respectively. Non-Watson-Crick base pairs would lead to mutations. In this report, we describe the ninth human DNA polymerase, Pol(iota), encoded by the RAD30B gene. We show that human Pol(iota) violates the Watson-Crick base-pairing rule opposite template T. During base selection, human Pol(iota) preferred T-G base pairing, leading to G incorporation opposite template T. The resulting T-G base pair was less efficiently extended by human Pol(iota) compared to the Watson-Crick base pairs. Consequently, DNA synthesis frequently aborted opposite template T, a property we designated the T stop. This T stop restricted human Pol(iota) to a very short stretch of DNA synthesis. Furthermore, kinetic analyses show that human Pol(iota) copies template C with extraordinarily low fidelity, misincorporating T, A, and C with unprecedented frequencies of 1/9, 1/10, and 1/11, respectively. Human Pol(iota) incorporated one nucleotide opposite a template abasic site more efficiently than opposite a template T, suggesting a role for human Pol(iota) in DNA lesion bypass. The unique features of preferential G incorporation opposite template T and T stop suggest that DNA Pol(iota) may additionally play a specialized function in human biology.
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PMID:Preferential incorporation of G opposite template T by the low-fidelity human DNA polymerase iota. 1098 26

Lesion bypass is an important mechanism to overcome replication blockage by DNA damage. Translesion synthesis requires a DNA polymerase (Pol). Human Pol iota encoded by the RAD30B gene is a recently identified DNA polymerase that shares sequence similarity to Pol eta. To investigate whether human Pol iota plays a role in lesion bypass we examined the response of this polymerase to several types of DNA damage in vitro. Surprisingly, 8-oxoguanine significantly blocked human Pol iota. Nevertheless, translesion DNA synthesis opposite 8-oxoguanine was observed with increasing concentrations of purified human Pol iota, resulting in predominant C and less frequent A incorporation opposite the lesion. Opposite a template abasic site human Pol iota efficiently incorporated a G, less frequently a T and even less frequently an A. Opposite an AAF-adducted guanine, human Pol iota was able to incorporate predominantly a C. In both cases, however, further DNA synthesis was not observed. Purified human Pol iota responded to a template TT (6-4) photoproduct by inserting predominantly an A opposite the 3' T of the lesion before aborting DNA synthesis. In contrast, human Pol iota was largely unresponsive to a template TT cis-syn cyclobutane dimer. These results suggest a role for human Pol iota in DNA lesion bypass.
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PMID:Response of human DNA polymerase iota to DNA lesions. 1116 Sep 25

Until recently, the molecular mechanisms of translesion DNA synthesis (TLS), a process whereby a damaged base is used as a template for continued replication, was poorly understood. This area of scientific research has, however, been revolutionized by the finding that proteins long implicated in TLS are, in fact, DNA polymerases. Members of this so-called UmuC/DinB/Rev1/Rad30 superfamily of polymerases have been identified in prokaryotes, eukaryotes and archaea. Biochemical studies with the highly purified polymerases reveal that some, but not all, can traverse blocking lesions in template DNA. All of them share a common feature, however, in that they exhibit low fidelity when replicating undamaged DNA. Of particular interest to us is the Rad30 subfamily of polymerases found exclusively in eukaryotes. Humans possess two Rad30 paralogs, Rad30A and Rad30B. The RAD30A gene encodes DNA polymerase eta and defects in the protein lead to the xeroderma pigmentosum variant (XP-V) phenotype in humans. Very recently RAD30B has also been shown to encode a novel DNA polymerase, designated as Pol iota. Based upon in vitro studies, it appears that Pol iota has the lowest fidelity of any eukaryotic polymerase studied to date and we speculate as to the possible cellular functions of such a remarkably error-prone DNA polymerase.
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PMID:DNA polymerase iota and related rad30-like enzymes. 1120 31

The human RAD30B gene has recently been shown to encode a novel DNA polymerase, DNA polymerase iota (poliota). The role of poliota within the cell is presently unknown, and the only clues to its cellular function come from its biochemical characterization in vitro. The aim of this short review is, therefore, to summarize the known enzymic activities of poliota and to speculate as to how these biochemical properties might relate to its in vivo function.
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PMID:Biochemical characterization of human DNA polymerase iota provides clues to its biological function. 1135 50