Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cyclin-dependent kinases cdk2 and cdk3 are required for the G1-S transition in mammalian cells. Here we show that G1 arrest induced by the corresponding dominant-negative mutants of these enzymes, cdk2dn or cdk3dn, is resistant to the action of SV40 T antigen (T). In the presence of cdk2dn, T released active E2F from negative control by pRb and its related family members (pocket proteins) but failed to induce S-phase. Therefore, among other targets, cdk2 also phosphorylates nonpocket protein substrates in promoting S-phase entry, and T does not mimic all cdk2 functions. In the presence of cdk3dn, however, T failed to induce cell cycle progression or stimulate E2F-dependent transcription activity. Dominant-negative cdk3 inhibited E2F-1, E2F-2, and, less significantly, E2F-3, but not E2F-4 transcription activity. The inhibition occurred in a pRb-independent manner and did not affect the DNA-binding capacity of the transcription factor. Cdk3 bound specifically to E2F-1/DP-1 complexes in vivo, most likely through DP-1. Thus, cdk3 function contributes to the activation of E2F-1, E2F-2, and partially E2F-3 and, thereby, participates in the process of S-phase entry.
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PMID:Differential effects of cdk2 and cdk3 on the control of pRb and E2F function during G1 exit. 884 21

Promoter elements that are important for the G1-S induction of the human thymidine kinase (htk) promoter reside within the core of the cell cycle regulatory unit, positioned between -110 and -84 upstream of the TATA element. Within this 27-bp region are three GC-rich motifs, which resemble the E2F binding site. By site-directed mutagenesis, we identified a 14-bp region, between -97 and -84, critical for the htk promoter transcriptional activity. Methylation interference studies indicate that the sequences between -97 and -84 are major protein contact points, correlating with the functional significance of this sequence in vivo. Although the core of the cell cycle regulatory unit contains three E2F-like sites and can form minor S-phase-specific complexes containing p107, cyclin A, and cdk2, the major complex that binds to this region is not competed by E2F binding sites. Through DNA affinity chromatography, we identified a set of protein species of approximately 40 kDa that copurified with the htk DNA binding activity. From gel shift assays and Western blot analysis, this protein species is antigenically distinct from E2F-1, E2F-2, E2F-3, and E2F-4. Our studies raise the possibility that other members of the E2F protein family or a novel protein(s) with preferred binding affinity for the htk promoter exert(s) control on the G1 to S regulation of the htk promoter through their interactions with cyclins and kinases.
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PMID:Identification of a set of protein species approximately 40 kDa as high-affinity DNA binding factor(s) to the cell cycle regulatory region of the human thymidine kinase promoter. 895 43

BRCA1, a familial breast and ovarian cancer susceptibility gene encodes nuclear phosphoproteins that function as tumor suppressors in human breast cancer cells. Previously, we have shown that overexpression of a BRCA1 splice variant BRCA1a accelerates apoptosis in human breast cancer cells. In an attempt to determine whether the subcellular localization of BRCA1 is cell cycle regulated, we have studied the subcellular distribution of BRCA1 in asynchronous and growth arrested normal, breast and ovarian cancer cells using different BRCA1 antibodies by immunofluorescence and immunohistochemical staining. Upon serum starvation of NIH3T3, some breast and ovarian cancer cells, most of the BRCA1 protein redistributed to the nucleus revealing a new type of regulation that may modulate the activity of BRCA1 gene. We have also characterized two new variant BRCA1 proteins (BRCA1a/p110 and BRCA1b/ p100) which are phosphoproteins containing phosphotyrosine. Immunofluorescence and Western blotting analysis indicate cytoplasmic and nuclear localization of BRCA1a and BRCA1b proteins. To elucidate the biological function of BRCA1, we created a bacterial fusion protein of glutathione-transferase (GST) and BRCA1 zinc finger domain and detected two cellular proteins with molecular weights of approximately 32 and 65 kD, one of which contains phosphotyrosine designated p32 and p65 BRCA1 interacting proteins (BIP) that specifically interact with BRCA1. Western blot analysis of BIP with cyclins/CDKs and E2F antisera indicated association with cdc2, cdk2, cdk4, cyclin B, cyclin D, cyclin A and E2F-4 but not with cdk3, cdk5, cdk6, E2F-1, E2F-2, E2F-3, E2F-5 and cyclin E. Furthermore, we have also demonstrated a direct interaction of in vitro translated BRCA1a and BRCA1b proteins with recombinant cyclin A, cyclin B1, cyclin D1, cdc2, cdk2 and E2F fusion proteins in vitro. Taken together these results seem to suggest that BRCA1 could be an important negative regulator of cell cycle that functions through interaction with E2F transcriptional factors and phosphorylation by cyclins/cdk complexes with the zinc ring finger functioning as a major protein-protein interaction domain. If the interactions we observe in vitro is also seen in vivo then it may be possible that lack or impaired binding of the disrupted BRCA1 proteins to E2F, cyclins/CDKs in patients with mutations in the zinc finger domain could deprive the cell of an important mechanism for braking cell proliferation leading to the development of breast and ovarian cancers.
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PMID:BRCA1 proteins are transported to the nucleus in the absence of serum and splice variants BRCA1a, BRCA1b are tyrosine phosphoproteins that associate with E2F, cyclins and cyclin dependent kinases. 924 50

We previously demonstrated that P16Ink4a (p16) expression in p16-deficient U343 astrocytoma cells causes a G1 cell cycle arrest, profound changes in cytoskeletal proteins and alterations in expression and activity of the pRB and E2F family proteins. We examine here the effects of expressing wild type or mutant versions of the downstream targets of p16 in U343 astrocytomas. We first attempted to block proliferation of U343 cells using the dominant mutant of pRB, deltap34. Expression of this mutant in the human osteosarcoma, SAOS-2, potently blocked proliferation but did not affect the cell cycle of U343 cells. We next showed that expression of E2F-1, E2F-2, E2F-3 and E2F-4 are each able to overcome this p16-dependent cell cycle arrest but exhibit distinct biological activities. Adenoviral-mediated expression of E2F-1, E2F-2, E2F-3, or E2F-4 overcame the p16-dependent cell cycle block and induced alterations in cell morphology. E2F-5, only in conjunction with DP1, promoted cell cycle progression. For both E2F-1 and E2F-2, but not E2F-3 or E2F-5/DP1, cell cycle re-entry was associated with almost quantitative cell death. Only small numbers of dying cells were observed in E2F-4-expressing cultures. Expression of the different E2F's altered the expression of distinct sets of cell cycle regulatory proteins. E2F-1 induced endogenous E2F-4 expression and also caused an increase in pRB, p107 and cyclin E levels. Expression of E2F-4 caused a weak increase in E2F-1 levels but also strongly induced pRB, p107, p130 and cyclin E. However, E2F-1 and E2F-4 clearly regulate expression of distinct genes, demonstrated when E2F-4 caused a threefold increase in the levels of cdk2 whereas E2F-1 failed to increase in this cyclin dependent kinase. Similarly, expression of E2F-1 or E2F-2 were shown to have distinct effects on the expression of cdk2, cyclin E and pRB despite both of these closely related E2F-family members potently inducing cell death. Thus, E2F-1, E2F-2, E2F-3 and E2F-4 are able to overcome the p16-dependent proliferative block in U343 astrocytoma cells. While overcoming this cell cycle block, each of the E2F's uniquely affect the expression of a number of cell cycle regulatory proteins and have distinct abilities to promote cell death.
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PMID:The E2F-family proteins induce distinct cell cycle regulatory factors in p16-arrested, U343 astrocytoma cells. 978 3