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 p107 protein is related to the Rb protein by a 60-kDa region of homology called the pocket domain that binds cellular proteins such as E2F and cyclins A and E as well as the viral oncoproteins E1A, E7, and SV40 T antigen. The p107 and Rb proteins have both been implicated as negative regulators of cell growth. We have examined the effect of the unphosphorylated pocket domain of p107 on specific stages of the T antigen-mediated replication of SV40 DNA in vitro. The pocket domain inhibited replication by preventing the assembly of T antigen at the SV40 core origin DNA containing binding site II. However, both proteins formed a ternary complex with DNA containing T antigen-binding site I. The pocket domain of p107 did not inhibit the oligomerization of T antigen in the absence of DNA, and the p107 derivative is bound to the intermediates of this reaction. In the unwinding assay, once T antigen was preassembled as hexamers at the core origin, the pocket domain bound to and stabilized the complex, resulting in an increase in the yield of unwound product. Preformed T antigen hexamers complexed with the pocket domain bind to a synthetic replication fork, and this complex supported unwinding. Consistent with this, the p107 pocket domain had no effect on the helicase activity of T antigen in an assay using a partial duplex substrate. However, a complex containing p107 and T antigen assembled at the core origin did not support SV40 DNA replication in HeLa cell crude extracts or in the monopolymerase reaction. This inhibition is due to the inability of the complex to bind to DNA polymerase alpha, which is required for the initiation of DNA synthesis. The data suggest pathways by which the pocket domain of p107 can negatively regulate T antigen-mediated replication in vitro. The binding of T antigen to p107 is discussed with respect to its role in mitigating negative cell growth control, resulting in viral mediated transformation.
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PMID:Initiation of DNA replication by simian virus 40 T antigen is inhibited by the p107 protein. 812

The Epstein-Barr Virus (EBV) immediate-early protein BRLF1 is one of two transactivators which mediate the switch from latent to lytic replication in EBV-infected cells. DNA viruses often modulate the function of critical cell cycle proteins to maximize the efficiency of virus replication. Here we have examined the effect of BRLF1 on cell cycle progression. A replication-deficient adenovirus expressing BRLF1 (AdBRLF1) was used to infect normal human fibroblasts and various epithelial cell lines. BRLF1 expression induced S phase entry in contact-inhibited fibroblasts and in the human osteosarcoma cell line U-2 OS. AdBRLF1 infection produced a dramatic increase in the level of E2F1 but not E2F4. In contrast, the levels of Rb, p107, and p130 were decreased in AdBRLF1-infected cells. Electrophoretic mobility shift assays confirmed an increased level of free E2F1 in the AdBRLF1-infected human fibroblasts. Consistent with the previously described effect of E2F1, AdBRLF1-infected fibroblasts had increased levels of p53 and p21 and died by apoptosis. BRLF1-induced activation of E2F1 may be required for efficient EBV lytic replication, since at least one critical viral replication gene (the viral DNA polymerase) is activated by E2F (C. Liu, N. D. Sista, and J. S. Pagano, J. Virol. 70:2545-2555, 1996).
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PMID:The Epstein-Barr virus protein BRLF1 activates S phase entry through E2F1 induction. 1040 Jul 50

Human p29 is a newly identified nuclear protein whose function is largely undetermined. We found that p29 associated with chromatin, interacted with MCM3, and localized with proliferating cell nuclear antigen foci in the S phase. Silencing of p29 using small interfering RNA duplexes reduced DNA synthesis and increased the expression of p107, a member of the RB family, and of cyclin-dependent kinase inhibitor p21, accompanied with a decreased expression of DNA polymerase alpha. Lethal events consisting of premature chromatin condensation with a reduced Chk1 phosphorylation were observed in p29-depleted cells in response to UV irradiation. Intriguingly, the phosphorylation of ataxia telangectasia-mutated kinases at S1981 was suppressed in p29-depleted HeLa cells with UV irradiation, but not in hydroxyurea- and ionizing radiation-treated cells. Taken together, these results reveal a novel function of p29 in the regulation of DNA replication checkpoint responses.
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PMID:Silencing of p29 affects DNA damage responses with UV irradiation. 1695 Nov 60