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

Previous experiments have demonstrated that the regulation of E2F-1 transcription factor activity is critical for the maintenance of normal cell proliferation control. Regulation of E2F-1 is accomplished through at least two mechanisms: posttranslational regulation by binding proteins such as Rb and transcriptional regulation of the E2F-1 gene. The E2F-1 gene promoter has recently been isolated to examine this latter aspect of E2F-1 regulation. Preliminary studies demonstrate that the E2F-1 promoter is under E2F-dependent negative control during the cell growth response, being transcriptionally repressed through E2F sites in G0 and early G1. We now demonstrate that the presence of an E2F DNA-binding complex containing the Rb-related p130 protein (Rb2) correlates with E2F-1 gene repression and that overexpression of p130 inhibits transcription from the E2F-1 promoter. Moreover, D-type cyclin-dependent kinase activity specifically activates the E2F-1 promoter by relieving E2F-mediated repression but is inhibited by coexpression of the cdk4 and cdk6 inhibitor p16 (CDKN2, MTS1, INK4). Taken together, these findings suggest that E2F-1 gene expression is controlled during cell cycle progression by a regulatory network involving at least one oncogene (cyclin D1) and several potential tumor suppressor genes.
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PMID:Regulation of E2F-1 gene expression by p130 (Rb2) and D-type cyclin kinase activity. 747 95

The retinoblastoma-related protein p130 is a putative negative regulator of cell proliferation in mammalian cells. In this study, p130 is shown to exist in multiple phosphorylated forms in human cells. In glioblastoma T98G cells synchronized by serum deprivation, specific phosphorylated forms of p130 are found at different times after serum re-stimulation. Two phosphorylated forms of p130 only found in serum-arrested T98G cells and in early G1 phase associate with the adenovirus oncoprotein E1A in vitro. One of these two forms corresponds to the in vivo E1A-associated p130 in 293 cells, which express endogenous E1A protein. Moreover, p130 undergoes an abrupt shift to a unique phosphorylated form in mid G1 which is the only p130 form found during the remaining phases of the cell cycle. This phosphorylated form possesses an associated histone H1 kinase activity that is most active in late S phase and G2/M. The cell cycle-dependent expression pattern of cyclins in T98G cells is compatible with cyclin D1/CDK complexes driving the shift to this phosphorylated p130 form in mid G1. These results suggest that the putative growth inhibitory function of p130 is regulated by phosphorylation of this protein. They also suggest that differential phosphorylation of p130 during the cell cycle plays distinct roles in the regulation of p130 function.
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PMID:Cell cycle-dependent phosphorylation of the retinoblastoma-related protein p130. 765 44

We identified a novel human nucleolar phosphoprotein p130 (130 kDa) using a strategy for selecting monoclonal antibodies against nuclear proteins which oscillate in the cell cycle. p130 is localized in interphase nucleoli in a dotted manner. Complete extraction of p130 required a high concentration of salt (0.5 M NaCl) indicating that it binds firmly to the nucleolar components via ionic interaction. p130 is heavily phosphorylated, since alkaline phosphatase treatment converted the purified p130 into a 95 kDa product; this was further supported by the in vitro demonstration that cellular phosphatase and casein kinase II activities were responsible for the interchange of these two forms. Extracts of mitotic cells had lower concentrations of p130 compared to those of interphase cells suggesting that a proportion of p130 might be degraded during mitosis. Moreover, all the remaining p130 in mitotic cells was further phosphorylated, likely by a cdc2 kinase, resulting in increase in its solubility, and its dispersion throughout the entire cytoplasm. Thus, p130 in metaphase and anaphase cells was unable to be detected by immunofluorescence microscopy. At telophase, p130 reappeared and aggregated into a granular structure, resembling the prenucleolar bodies. These granules migrated from the nucleoplasm to the nucleoli in early G1-phase. Actinomycin D was able to induce segregation of p130-containing granules into the nucleoplasm, similar to the well-known behavior of the fibrillarin-containing granules, indicating that p130 is localized in the dense fibrillar component, a subnucleolar region for pre-rRNA synthesis and processing. The cDNA sequence of p130 revealed a remarkable feature, that a serine-rich stretch interspersed with acidic residues is repeated ten times. Such a characteristic is shared with a rat nucleolar phosphoprotein Nopp140, which is thought to shuttle between the nucleolus and the cytoplasm. Although p130 shows 74% identity to Nopp140, our observations suggest that during mitosis the functions of p130 are related to nucleologenesis.
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PMID:Cell-cycle-dependent alterations of a highly phosphorylated nucleolar protein p130 are associated with nucleologenesis. 765 14

The activities of E2F transcription factors are inhibited by interactions with members of the retinoblastoma (RB) tumor suppressor family, p105RB, p107 and p130. In cycling cells p107 and p130 also interact with heterodimers comprised of Cdk2 and either A or E cyclins. We characterized E2F complexes present in C2C12 and P19 mouse cells induced to differentiate into muscle and neuronal cells, respectively. In both undifferentiated C2C12 and P19 cells, in addition to free species, E2F was found in complexes containing p107 or p130 and Cdk2. No E2F-pRB complexes were detected by electrophoretic mobility shift assays even though such cells were shown to contain pRB and E2F species capable of interacting in vitro. These results suggested that although present, pRB was unable to interact with E2F. Following differentiation of C2C12 cells into myotubes, E2F was present in at least two complexes which contained p130, but not in those containing p107 or Cdk2. Low levels of E2F-pRB complexes were also detected in fully differentiated C2C12 myotubes and in freshly isolated skeletal muscle. In the case of differentiated P19 neuronal cells, E2F was found in complexes containing pRB, p107 and p130. However, such cells may not be representative of fully differentiated neurons, as studies with rodent brain extracts indicated that only pRB-E2F complexes and those recognized by a p130-specific serum were present. These results suggested that in both muscle and neurons, pRB and p130 may play specific roles in the development or maintenance of terminal differentiation.
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PMID:Characterization of transcription factor E2F complexes during muscle and neuronal differentiation. 767 50

The p130 protein is a recently cloned member of the retinoblastoma protein family. We show here that transformation of NIH3T3-L1 fibroblasts (L1 cells) by the simian virus 40 large T antigen (LTAg) depends on the disruption of DNA binding complexes between transcription factor E2F and p130. LTAg binds to the pocket region of p130 in vivo and disrupts the E2F-p130 complexes. E2F-p130 complexes are present only in quiescent L1 cells and disappear at the G1/S phase boundary concomitantly to induction of DNA synthesis and expression of the E2F-regulated cdc2 gene. p130 is a substrate of cyclin-dependent kinase 2 (Cdk2) in vitro and associates with a Cdk in vivo which is activated upon serum stimulation in late G1. Overexpression of p130 inhibits cdc2 promoter activity and entry of quiescent L1 cells into S phase. The results demonstrate that p130 is negative regulator of cell cycle progression which is specifically targeted by LTAg during cell transformation.
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PMID:A complex between E2F and the pRb-related protein p130 is specifically targeted by the simian virus 40 large T antigen during cell transformation. 778 51

Transforming growth factor beta 1 (TGF-beta 1) is known to inhibit epithelial cell growth by inducing a G1 cell cycle arrest. We have studied the effect of TGF-beta 1 on protein binding to a transcription factor E2F consensus element in extracts from early passage human keratinocytes (HFKs) and a permanent human keratinocyte cell line (HaCaT). Treatment of these cells with TGF-beta 1 resulted in the formation of a DNA binding complex between the pRb-related protein p130 and E2F. Formation of the E2F-p130 complex correlated with inhibition of cell cycle progression in G1 and suppression of the E2F-regulated cdc2 gene. While p130 mRNA and protein levels were not influenced by TGF-beta 1, the activity of cyclin-dependent kinase 2 (Cdk2) towards p130 in vitro was inhibited. The results identify p130 as a downstream target of TGF-beta 1 and a possible mediator of the G1 cell cycle arrest.
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PMID:The pRb-related protein p130 is a possible effector of transforming growth factor beta 1 induced cell cycle arrest in keratinocytes. 778 52

Association of the E2F transcription factor with the pRb and p107 proteins appears to regulate the activity of E2F and, in turn, affect cell cycle progression. We found, however, that pRb and p107 are only minor E2F-associated proteins in G0/G1 mouse fibroblasts, and we sought to identify the major E2F partner protein in these cells. Because the adenovirus E1A oncoprotein seemed able to bind to the G0 E2F partner, we enriched for proteins that associated both with an E2F-binding site DNA column and with E1A. The major species in G0 and early G1 fibroblasts detected with this approach had properties identical to the pRb- and p107-related p130 protein. In serum-stimulated cells, p107 replaced p130 as the major E2F-associated protein near the G1/S border, concomitant with an increase in p107 protein levels. p130-E2F complexes resembled p107-E2F complexes in their ability to bind to cyclin-cdk kinases, and they appeared to be associated with the cyclin E-cdk2 kinase in late G1 cells. These observations indicate that E2F transcription factors are regulated by a succession of partner proteins with which they associate during defined stages of the cell cycle.
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PMID:Cell cycle-specific association of E2F with the p130 E1A-binding protein. 825 85

In quiescent cells, cdc2 mRNA is almost undetectable. Stimulation of cells to reenter the cell cycle results in induction of cdc2 expression, beginning at the G1-to-S transition and reaching maximum levels during late S and G2 phases. To investigate cdc2 transcriptional regulation throughout cell cycle progression, we monitored protein-DNA interactions by in vivo footprinting along 800 bp of the human cdc2 promoter in quiescent fibroblasts and at different time points following serum stimulation. We found 11 in vivo protein-binding sites, but no protein binding was observed at a high-affinity E2F site that had previously been implicated in cdc2 regulation. Nine of the identified in vivo binding sites (among them were two inverted CCAAT boxes, two Sp1 sites, and one ets-2 site) bind transcription factors constitutively throughout the cell cycle. However, at two elements located at positions -60 and -20 relative to the transcription start site, the binding pattern changes significantly as the cells are entering S phase. A G0- and G1-specific protein complex disappears at the -20 element at the beginning of S phase. This sequence deviates at one base position from known E2F consensus binding sites. We found that the major E2F activity in human fibroblasts contains E2F-4 and p130. The -20 element of the cdc2 gene specifically interacts with a subset of E2F-4-p130 complexes present in G0 cells but does not interact with S-phase-specific E2F complexes. Transient-transfection experiments with wild-type and mutant cdc2 promoter constructs indicate that the -20 element is involved in suppressing cdc2 activity in quiescent cells. We suggest that the presence of the p130-E2F-4 complex in G0/G1 blocks access of components of the basal transcription machinery or prevents transaction by the constitutively bound upstream activator proteins.
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PMID:In vivo structure of the human cdc2 promoter: release of a p130-E2F-4 complex from sequences immediately upstream of the transcription initiation site coincides with induction of cdc2 expression. 852 57

The E6 and E7 proteins of the high-risk human papillomaviruses (HPVs) act coordinately to immortalize human keratinocytes. These viral oncoproteins function by binding and altering the activity of cellular proteins which regulate cell cycle progression. Among the proteins bound by E7 are the retinoblastoma protein, Rb, as well as the related p107 and p130 proteins. In addition, E7 binds cyclin A, which regulates transit through the S and G2/M phases of the cell cycle. In this study, we demonstrate that HPV 18 E7 also associates with cyclin E which controls the G1/S transition. E7/cyclin E complexes were immunoprecipitated from E7-expressing cells as well as from cell extracts using GST-E7 fusion proteins. E7 was found to complex with a single form of cyclin E, and the binding was mediated through p107. Both E7/cyclin E and E7/cyclin A complexes exhibit kinase activity through associated cdk2 proteins which can contribute to phosphorylation of p107. The association of E7 with proteins which regulate transit through the cell cycle may provide an additional mechanism by which infection with human papillomaviruses results in cellular hyperproliferation.
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PMID:Human papillomavirus E7 oncoproteins bind a single form of cyclin E in a complex with cdk2 and p107. 855 88

In nonproliferating or growth-arrested cells, the transcription factor E2F remains bound to the retinoblastoma-related protein p130. Accumulation of this E2F-p130 complex correlates with an arrest of the cell cycle progression. Progression through G1 phase is associated with a cyclin-dependent binding of the cyclin-dependent kinase cdk2 to the E2F-p130 complex. By fractionating mouse L-cell extracts, we have obtained a partially purified preparation of the E2F-p130 complex that also contains cdk2. Incubation of this complex with recombinant p21 results in a disruption of the interaction between cdk2 and the E2F-p130 complex in extracts of a cell line that expresses a temperature-sensitive mutant of p53. Incubation at the permissive temperature (32 degrees C) results in an induction of p21 synthesis. An increase in the level of p21 in these cells correlates with a loss of cdk2 from the cdk2-containing E2F-p130 complex. We also show that the expression of a reporter gene containing E2F sites in the promoter region is reduced by the coexpression of p21. Since p21 is believed to be a mediator of p53, we speculated that the p21-mediated disruption of the cdk2-containing E2F-p130 complex plays a role in the growth suppression function of p53.
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PMID:p21 Disrupts the interaction between cdk2 and the E2F-p130 complex. 862 74


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