Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

DNA polymerase alpha activity was determined following serum stimulation of early and late passages of human diploid fibroblast-like (HDFL) cultures derived from apparently normal donors (two strains) and from a patient with Werner's syndrome (one strain). Induction of this enzyme was observed in both low passage, actively proliferating cultures and in postmitotic "senescent" cultures from all three strains. The maximal polymerase activity of early and late passage cells of each strain were nearly identical when normalized to the number of cells present. However, the activity of the enzyme was observed to be significantly lower in late passage cultures when normalized to total protein content apparently because of enlargement of the senescent cells. The behavior of Werner derived cells was similar to that of the normal cells. The induction of DNA polymerase alpha in senescent cultures indicates that they retain the capacity to carry out some complex metabolic responses to mitogen stimulation. In addition, these results suggest the possibility that dilution of DNA polymerase alpha and/or other DNA replication factors may play a role in the onset or maintenance of the postmitotic state in the enlarged senescent HDFL cells.
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PMID:Induction of DNA polymerase alpha in senescent cultures of normal and Werner's syndrome cultured skin fibroblasts. 393 May 24

Werner syndrome (WS) is a rare autosomal recessive disorder characterized by prematurely aged appearance. Genetic linkage analysis has placed the relevant gene in subchromosomal band 8p12. DNA polymerase beta gene has been mapped to chromosome 8p12-11 and thought to be involved in DNA repair and possibly in recombination. Somatic cells from WS patients exhibit chromosomal instability, a markedly reduced replicative life span and slow growth. The functions of DNA polymerase beta gene and its position prompted us to examine this gene in WS patients. We have found the novel DNA polymerase beta cDNA species in blood samples from WS patients, which contain 107 bp insertions or 87 bp deletions in the catalytic domain of DNA polymerase beta. These mutations change the structure of DNA polymerase beta and thus the capacity of the DNA repair system would be impaired, which may account for the high mutation rate observed in WS.
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PMID:Identification of mutations in DNA polymerase beta mRNAs from patients with Werner syndrome. 754 22

Werner syndrome (WS) is a rare autosomal recessive disorder of humans characterized by the premature onset and accelerated rate of development of several major age-related disorders. An aberration in DNA replication or repair is suggested by the evidence of genome instability. Since the structural gene for DNA polymerase beta maps within the region of the WS mutation on the short arm of chromosome 8 and is involved in both DNA repair and DNA replication, we evaluated its candidacy as the WS gene. Several independent lines of evidence did not support that hypothesis: (1) activity gels showed normal enzyme activity and electrophoretic mobility; (2) nucleotide sequence analysis of the entire coding region failed to reveal mutations (although indicated mistakes in the published sequence); (3) single-strand conformation polymorphism (SSCP) and heteroduplex analyses failed to reveal evidence of mutations in the promoter region; (4) a newly discerned polymorphism failed to reveal evidence of homozygosity by descent in a consanguineous patient; and 5) fluorescence in situ hybridization (FISH) analysis placed the DNA polymerase beta gene centromeric to D8S135 at 8p11.2 and thus beyond the region of peak LOD scores for WS.
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PMID:Evidence against DNA polymerase beta as a candidate gene for Werner syndrome. 816 25

Mammalian DNA polymerase beta is a crucial enzyme in cell genomic maintenance. Its structure is highly conserved. Some splice variants of beta-pol mRNA were observed. One alternative splice DNA polymerase beta mRNA, generated by 87 nt deletion (exon 11) in the catalytic domain of this enzyme, was suggested to be responsible for genomic instability in tumorigenesis and in genetic disorder (Werner syndrome). Here, we show that exon-11-deleted beta-pol mRNA is present in all examined normal and tumor tissues as well as in resting or PHA-stimulated peripheral-blood mononuclear cells. This finding proves that the presence of the exon-11 alternative splicing variant of beta-pol mRNA is not tumor-specific.
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PMID:Alternative splicing of DNA polymerase beta mRNA is not tumor-specific. 890 Apr 28

Positional cloning has already produced the sequences of more than 70 human genes associated with specific diseases. In addition to their medical importance, these genes are of interest as a set of human genes isolated solely on the basis of the phenotypic effect of the respective mutations. We analyzed the protein sequences encoded by the positionally cloned disease genes using an iterative strategy combining several sensitive computer methods. Comparisons to complete sequence databases and to separate databases of nematode, yeast, and bacterial proteins showed that for most of the disease gene products, statistically significant sequence similarities are detectable in each of the model organisms. Only the nematode genome encodes apparent orthologs with conserved domain architecture for the majority of the disease genes. In yeast and bacterial homologs, domain organization is typically not conserved, and sequence similarity is limited to individual domains. Generally, human genes complement mutations only in orthologous yeast genes. Most of the positionally cloned genes encode large proteins with several globular and nonglobular domains, the functions of some or all of which are not known. We detected conserved domains and motifs not described previously in a number of proteins encoded by disease genes and predicted functions for some of them. These predictions include an ATP-binding domain in the product of hereditary nonpolyposis colon cancer gene (a MutL homolog), which is conserved in the HS90 family of chaperone proteins, type II DNA topoisomerases, and histidine kinases, and a nuclease domain homologous to bacterial RNase D and the 3'-5' exonuclease domain of DNA polymerase I in the Werner syndrome gene product.
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PMID:Positionally cloned human disease genes: patterns of evolutionary conservation and functional motifs. 915

Individuals with mutations in the WRN gene suffer from Werner syndrome, a disease with early onset of many characteristics of normal aging. The WRN protein (WRNp) functions in DNA metabolism, as the purified polypeptide has both 3'-->5' helicase and 3'-->5' exonuclease activities. In this study, we have further characterized WRNp exonuclease activity by examining its ability to degrade double-stranded DNA substrates containing abnormal and damaged nucleo-tides. In addition, we directly compared the 3'-->5' WRNp exonuclease activity with that of exo-nuclease III and the Klenow fragment of DNA polymerase I. Our results indicate that the presence of certain abnormal bases (such as uracil and hypoxanthine) does not inhibit the exonuclease activity of WRNp, exo-nuclease III or Klenow, whereas other DNA modifications, including apurinic sites, 8-oxoguanine, 8-oxoadenine and cholesterol adducts, inhibit or block WRNp. The ability of damaged nucleo-tides to inhibit exonucleolytic digestion differs significantly between WRNp, exonuclease III and Klenow, indicating that each exonuclease has a distinct mechanism of action. In addition, normal and modified DNA substrates are degraded similarly by full-length WRNp and an N-terminal fragment of WRNp, indicating that the specificity for this activity lies mostly within this region. The biochemical and physiological significance of these results is discussed.
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PMID:Selective blockage of the 3'-->5' exonuclease activity of WRN protein by certain oxidative modifications and bulky lesions in DNA. 1090 33

N,N'-Bis[2-(1-piperidino)ethyl]-3,4,9,10-perylenetetracarboxylic diimide (PIPER), a perylene derivative, is a very potent and selective G-quadruplex DNA-interactive agent. It has been shown to inhibit DNA polymerase and telomerase by stacking externally to the G-tetrads in the G-quadruplex structures. Recently, we have demonstrated that this small molecule greatly accelerates the assembly of G-quadruplex structures in a cell-free system. In this report, we present data demonstrating that PIPER prevents the unwinding of G-quadruplex structures by yeast Sgs1 helicase. Sgs1 belongs to the RecQ DNA helicase family whose members include other G-quadruplex DNA unwinding helicases, such as human Bloom's syndrome and human Werner's syndrome helicases. PIPER specifically prevents the unwinding of G-quadruplex DNA but not duplex DNA by Sgs1. Competition experiments indicate that this inhibitory activity is due to the interaction of PIPER with G-quadruplex structures rather than the helicase itself. These results combined with previous studies suggest a possible mechanism of action for these G-quadruplex-interactive agents inside cells: they might induce G-quadruplex formation in G-rich regions on genomic DNA, stabilize these structures, and prevent them from being cleared by enzymes such as helicases. The G-quadruplex structures may, in turn, disrupt some critical cellular events such as DNA replication, transcription regulation, and telomere maintenance.
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PMID:Inhibition of unwinding of G-quadruplex structures by Sgs1 helicase in the presence of N,N'-bis[2-(1-piperidino)ethyl]-3,4,9,10-perylenetetracarboxylic diimide, a G-quadruplex-interactive ligand. 1092 24

Werner syndrome is a Mendelian disorder of man that produces a number of manifestations resembling human aging. This disorder is caused by inactivation of the wrn gene, a member of the RecQ family of DNA helicases. The helicase and exonuclease activities of the Werner protein (WRN) suggest that it functions in DNA transactions, but the physiological function of WRN remains elusive. We present several lines of evidence that WRN interacts specifically with the p50 subunit of polymerase delta, the major DNA polymerase required for chromosomal DNA replication. P50, identified by yeast two-hybrid screening, interacts physically with the C terminus of WRN. Native WRN protein coimmunoprecipitates with p50 in a cellular fraction enriched in nucleolar proteins, and this immunocomplex also includes p125, the catalytic subunit of polymerase delta. In subcellular localization studies of cells transfected with WRN, p50 and p125 redistribute to the nucleolus and colocalize with WRN. These results suggest that one of the functions of WRN protein is to directly modify DNA replication via its interaction with p50 and abet dynamic relocalization of the DNA polymerase delta complexes within the nucleus.
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PMID:Werner protein recruits DNA polymerase delta to the nucleolus. 1102 36

Werner syndrome is a hereditary premature aging disorder characterized by genomic instability. Genetic analysis and protein interaction studies indicate that the defective gene product (WRN) may play an important role in DNA replication, recombination, and repair. DNA polymerase beta (pol beta) is a central participant in both short and long-patch base excision repair (BER) pathways, which function to process most spontaneous, alkylated, and oxidative DNA damage. We report here a physical interaction between WRN and pol beta, and using purified proteins reconstitute of a portion of the long-patch BER pathway to examine a potential role for WRN in this repair response. We demonstrate that WRN stimulates pol beta strand displacement DNA synthesis and that this stimulation is dependent on the helicase activity of WRN. In addition, a truncated WRN protein, containing primarily the helicase domain, retains helicase activity and is sufficient to mediate the stimulation of pol beta. The WRN helicase also unwinds a BER substrate, providing evidence that WRN plays a role in unwinding DNA repair intermediates. Based on these findings, we propose a novel mechanism by which WRN may mediate pol beta-directed long-patch BER.
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PMID:The Werner syndrome protein stimulates DNA polymerase beta strand displacement synthesis via its helicase activity. 1266 21

The 3'-5' riboexonuclease Rrp6p, a nuclear component of the exosome, functions with other exosome components to produce the mature 3' ends of 5.8S rRNA, sno- and snRNAs, and to destroy improperly processed precursor (pre)-rRNAs and pre-mRNAs. Rrp6p is a member of the RNase D family of riboexonucleases and displays a high degree of homology with the active site of the deoxyriboexonuclease domain of Escherichia coli DNA polymerase I, the crystal structure of which indicates a two-metal ion mechanism for phosphodiester bond hydrolysis. Mutation of each of the conserved residues predicted to coordinate metal ions in the active site of Rrp6p abolished activity of the enzyme in vitro and in vivo. Complete loss of Rrp6p activity caused by the Y361F and Y361A mutations supports the critical role proposed for the phenolic hydroxyl of Tyr361 in the reaction mechanism. Rrp6p also contains an helicase RNase D C-terminal (HRDC) domain of unknown function that is similar to domains in the Werner's and Bloom's Syndrome proteins. A point mutation in this domain results in Rrp6p that localizes to the nucleus, but fails to efficiently process the 3' ends of 5.8S pre-rRNA and some pre-snoRNAs. In contrast, this mutant retains the ability to degrade rRNA processing intermediates and 3'-extended, poly(A)+ snoRNAs. These findings indicate the potential for independent control of the processing and degradation functions of Rrp6p.
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PMID:Contribution of domain structure to the RNA 3' end processing and degradation functions of the nuclear exosome subunit Rrp6p. 1292 58


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