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 single-stranded DNA binding protein RP-A is required in SV40 DNA in vitro replication. The RP-A purified from calf thymus contains 4 polypeptides with molecular weights 70kDa, 53kDa, 32kDa, and 14kDa. The p70 subunit and its proteolysed form p53 are recognized by the monoclonal antibody 70C (Kenny et al. (1990)) and bind to ssDNA. The p70 and p32 subunits of bovine RP-A are phosphorylated by CDC2-cyclin B kinase. Bovine RP-A supports the origin dependent unwinding of SV40 DNA by T antigen. Furthermore, bovine RP-A can efficiently substitute for human RP-A in SV40 DNA replication in vitro. A modified blotting technique revealed that RP-A interacts specifically and directly with the p48 subunit of DNA polymerase alpha-primase complex.
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PMID:Purification and functional characterization of bovine RP-A in an in vitro SV40 DNA replication system. 133 80

The mutagenic spectrum induced by aflatoxin-DNA lesions in DNA repair deficient and repair proficient human cells was investigated. The reactive metabolite aflatoxin B1-8,9-epoxide was synthesized and reacted in vitro with the shuttle vector plasmid pS189. Plasmids were transfected into human fibroblasts and allowed to replicate, and the recovered plasmids were screened in indicator bacteria for plasmid survival and mutations in the supF marker gene. Sequence data were obtained from 71 independently arising mutants recovered from DNA repair deficient xeroderma pigmentosum (XP) cells [XP12BE(SV40)] and 60 mutants recovered from a DNA repair proficient cell line (GM0637). Plasmid survival was lower and mutation frequency higher with the XP cells, and the mutation hotspots differed substantially for the 2 cell lines. Most mutations (> 90%) were base substitutions at G:C pairs, only about one-half of which were G:C-->T:A transversions, the expected predominant mutation. One-third of the mutations at GG sites and none of those at isolated Gs were G:C-->A:T transitions. Tandem base substitutions also occurred only at GG sites and were found only with XP cells. The location of mutation hotspots with either cell line did not correlate with the level of modification within the sequence as assessed by a DNA polymerase stop assay. These results suggest that the DNA repair deficiency associated with XP can influence not only the overall frequency of mutations but also the distribution of mutations within a gene. The finding of transition mutations exclusively at GG sites may be of predictive value in attempts to link dietary aflatoxin exposure to cancers associated with specific mutations in the c-ras oncogene and the p53 tumor suppressor gene.
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PMID:Sequence specificity of aflatoxin B1-induced mutations in a plasmid replicated in xeroderma pigmentosum and DNA repair proficient human cells. 139 91

Conditional expression of wild-type (wt) p53 protein in a glioblastoma tumor cell line has been shown to be growth inhibitory. We have now more precisely localized the position in the cell cycle where growth arrest occurs. We show that growth arrest occurs prior to or near the restriction point in late G1 phase of the cell cycle. The effect of wt p53 protein on the expression of four immediate-early genes (c-FOS, c-JUN, JUN-B, and c-MYC), one delayed-early gene (ornithine decarboxylase), and two late-G1/S-phase genes (B-MYB and DNA polymerase alpha) was also examined. Of this subset of growth response genes, only the expression of B-MYB and DNA polymerase alpha was significantly repressed. The possibility that decreased expression of B-MYB may be an important component of growth arrest mediated by wt p53 protein is discussed.
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PMID:Growth arrest induced by wild-type p53 protein blocks cells prior to or near the restriction point in late G1 phase. 140 26

The expression of p53 in colorectal tumors was studied immunohistochemically by monoclonal antibody (PAb1801). No nuclear staining was evident in the tumor cells of colorectal adenomas. p53 immunoreactivity was found in 59 (61.5%) of 96 colorectal cancers. There was no significant correlation between the p53 immunoreactivity and histologic type, tumor size, invasion of bowel wall, lymphatic invasion, venous invasion, lymph node metastasis, peritoneal dissemination, or liver metastasis. However, the p53 negative tumors showed a recurrence rate of 3.3%, while for the p53 positive tumors a recurrence rate of 20.9%. p53 negative tumors were associated with favorable prognosis, whereas those with p53 positive tumors were related to poor prognosis. DNA polymerase alpha positive cells rate in p53 positive tumors was significantly higher than in p53 negative tumors. The results suggested that p53 immunoreactivity might possibly be a useful prognostic marker of colorectal cancers.
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PMID:[Immunohistochemical detection of p53 in colorectal cancer and its relationship to prognosis]. 143 94

Increasing numbers of alterations have been found in protooncogenes (e.g., ras, myc), as well as tumor suppressor genes (e.g., p53, Rb) in various types of tumors. The multiple mutations cannot be explained by the spontaneous mutation rate. It has been suggested that mutator phenotypes leading to the accumulation of these mutations may be required in the early stages of tumorigenesis. To test this hypothesis, the entire coding region of DNA polymerase beta, a repair enzyme, mRNA from colorectal tumors, and corresponding normal mucosa were amplified by polymerase chain reaction, cloned, and sequenced. Mutations in the catalytic domain of DNA polymerase beta were detected in colorectal tumor specimens compared to the normal colorectal mucosa, placenta, and blood samples. Since these mutations changed the structure of polymerase beta, it is expected that the efficiency of the DNA repair system would be impaired and thus may account for the high mutation rate observed in colorectal carcinomas.
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PMID:DNA polymerase beta mutations in human colorectal cancer. 151 47

In lung and liver cancers, p53 mutations are mostly G:C to T:A transversions. This type of mutation is known to be induced by benzo(a)pyrene and aflatoxin B1 which are associated with the etiology of lung and liver cancers, respectively. Using a novel assay based on DNA polymerase fingerprint analysis, we identified p53 nucleotides targeted by these carcinogens. Thirteen of 14 nucleotide residues of the p53 gene which underwent G:C to T:A mutations in lung cancers were targeted by benzo(a)pyrene. Similarly, aflatoxin B1 formed adducts at a mutational hotspot specific for liver cancer. The same nucleotide (third base of codon 249), which mutates rarely in lung cancers, was not a target for benzo(a)pyrene. These in vitro observations indicate that p53 mutational hotspots identified in different tumors are selected targets specifically for the etiologically defined environmental carcinogens.
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PMID:Selective targeting of p53 gene mutational hotspots in human cancers by etiologically defined carcinogens. 193 77

Simian virus 40 large T antigen is the only viral protein required for SV40 DNA synthesis in vivo and in vitro. This complex protein recruits the cellular DNA replication apparatus to the SV40 origin and provides a good model for the initiation of cellular DNA replication. The interaction between SV40 large T antigen (TAg) and DNA polymerase alpha has been shown previously to be inhibited by murine p53, the nuclear protein product of a cellular anti-oncogene. The murine p53 protein will inhibit SV40 replication both in vivo and in vitro. Using monoclonal antibodies to TAg, p53, and polymerase alpha, we developed immunoassays to measure the complexes formed between TAg and polymerase alpha and between TAg and p53. The assays allowed us to detect the TAg-polymerase alpha and TAg-p53 complexes in lytically infected and transformed cells. The amount of TAg complexed to p53 was far lower in infected cells than in transformed cells. We used a large range of monoclonal antibodies to different sites on T antigen and found that antibodies that inhibited the formation of the TAg-polymerase alpha complex also inhibited the formation of the TAg-p53 complex. Finally, we found that the tsA58 and 5080 point mutations in TAg, previously shown to inhibit the binding of TAg to p53, also inhibit its binding to polymerase alpha. Together these results emphasize the specificity and functional importance of the TAg-polymerase alpha complex. The disruption of this interaction by the cellular anti-oncogene p53 provides an interesting model for the normal action of p53 and the effects of its removal on the regulation of cellular DNA synthesis.
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PMID:Interactions between SV40 T antigen and DNA polymerase alpha. 196 85

Flow cytometry (FCM) is a useful method for clinical research of oncogene products since it can analyze proteins quantitatively which are located at cell surfaces or inside of cells. Oncogene products are now under study by FCM not only as tumor markers but also as functioning proteins in carcinogenesis. The examples of oncogene products analyzed by FCM are ras, myc, p53, myb and fos; those of cell-proliferation-related proteins are Ki-67, PCNA and DNA polymerase alpha. In some diseases the relationship between these proteins and disease classification, stage, pathophysiology, or prognosis have been clarified. Using dual color FCM of H-ras p21 and DNA, we analyzed the expression of H-ras p21 in human multiple myeloma and leukemias and found that H-ras p21 levels in multiple myeloma strongly correlated to the prognosis of patients (p = 0.03). When AML cells were stimulated by adding G-CSF, it was found that many cells proliferated but some were dying. The percentage of dying cells was small in one AML case whose myeloblasts showed increased expression of H-ras p21 by G-CSF stimulation. Together with other papers reviewed, it is conceivable that H-ras p21 expression is related to cell proliferation and inhibition of cell autolysis. Thus FCM is useful in the classification of the role of oncogene products in carcinogenesis in clinical cases.
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PMID:[Application of flow cytometry to the study of hematologic disorders: analysis of oncogene products]. 214 49

Several nuclear and surface proteins are expressed in varying amounts in the different phases of the cell cycle. For some of them the coding gene is not known and changes in their expression could simply be secondary to changes in the proliferative activity of the population. Other proteins are oncogene products, probably having a direct regulatory function in cell proliferation, differentiation and malignant transformation. Studying these proteins may both permit a better understanding of the mechanisms regulating proliferation and differentiation and provide kinetic parameters for describing the cell cycle. Based on antibodies against these proteins, bivariate flow cytometry (FCM) is able to quantitate their expression simultaneously with DNA distribution. This allows protein expression to be related precisely with each cell cycle phase in populations having different proliferative activity. Further advantages of bivariate FCM are that few cells are required for the analysis and the percentage of cells expressing the (onco) gene product can be determined. Several cellular proteins have been investigated with bivariate FCM, and the data are reviewed. Some proteins not coded by oncogenes (such as cyclin, the Ki-67 reactive antigen and DNA polymerase alpha) are expressed in cycling, but not in G0 cells and are of special interest for the kineticist, since they could identify cells which are able to initiate DNA synthesis, i.e. those representing the "growth fraction" of the population. Statin, on the contrary, is apparently expressed only in G0 cells. The expression of some proteins coded by oncogenes, such as p53 and the c-myc product is high in proliferating G1 cells and decreases with differentiation. The expression of the c-ras product is not strictly related to cell cycle phases and increases with differentiation. Technical improvements (allowing, for example, the monitoring of the changes in protein expression following the microinjection of a protein-blocking substance into the cells and the inclusion of phenotype markers into the analysis) will expand the role of bivariate FCM for these research works.
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PMID:Cell cycle-related proteins and flow cytometry. 214 99

The effects of two different cell cycle inhibitors on the proliferation of human lymphoblastoid cells have been analyzed by flow cytometric techniques. Mimosine, a plant amino acid, reversibly blocks the cell cycle at a point which occurs roughly 2 h before the arrest mediated by aphidicolin, an inhibitor of DNA polymerase alpha activity, which defines the G1/S phase boundary. The levels of thymidine kinase mRNA, which increase at the onset of S phase, are higher in cells blocked with aphidicolin than in cells treated with mimosine whereas the opposite results are obtained in the case of p53 mRNA levels, which are known to be maximal in the late G1 phase. These results indicate that mimosine inhibits cell cycle traverse in the late G1 phase prior to the onset of DNA synthesis and identifies a previously undefined reversible cell cycle arrest point.
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PMID:A reversible arrest point in the late G1 phase of the mammalian cell cycle. 215 61


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