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)

In yeast, the protein kinase p34cdc2 plays a role in regulating both the G2 to M and G1 to S phase transitions. The discovery of multiple homologues of the protein in cells of higher eukaryotic organisms suggests that different cell cycle regulatory events may be performed by different kinases in such cells. Here, the synthesis and metabolism of the human forms of these proteins are described in a normal human cell type, peripheral blood T lymphocytes that have been stimulated to enter the cell cycle in vitro. Using a carboxyl-terminus antiserum specific for true p34cdc2, the protein could first be found in T cells at about 24 to 30 h after stimulation, just before the initiation of DNA synthesis. Three forms of the enzyme could be resolved by denaturing gel electrophoresis: an unphosphorylated form with an apparent molecular mass of 34,500 daltons and two phosphorylated derivatives. In cells synchronized at G2/M phase with nocodazole, p34 was almost entirely in the unphosphorylated form whereas the phosphorylated derivatives were more predominant in cultures arrested at the G1/S border with aphidicolin. The relationship of p34 synthesis to the phosphorylation of p110Rb, an event known to be associated with passage through late G1 and/or the G1/S phase transition, was also investigated. It was noted that p110Rb phosphorylation began before p34 synthesis first became detectable. Furthermore, it appeared that the two events could be largely uncoupled by treating cells with deferoxamine (10 microM), an iron chelating agent that arrests T cells at a point in late G1 phase but substantially before the G1 to S phase transition. Under these conditions, p110Rb phosphorylation was almost completely accomplished in the absence of significant p34 synthesis, a finding that suggests that most or all of p110 phosphorylation is performed by kinases other than p34. Because of this observation, extracts were next examined for p34-like molecules using an antibody against the so-called PSTAIRE domain found in all cdc2 homologues identified to date. A species of protein with a mobility slightly less than true p34 was found, even in resting T cells. Upon stimulation, this protein increased slightly in amount, and a second protein with a mobility greater than p34, a putative p33cdk2, was seen. Not only was the appearance of these proteins not inhibited by deferoxamine but they accumulated in cultures treated with the drug, suggesting that p33, and not p34, may be the G1 phase kinase for p110Rb.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Regulation of synthesis of p34cdc2 and its homologues and their relationship to p110Rb phosphorylation during cell cycle progression of normal human T cells. 154 21

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

The p58(PITSLRE) is a p34(cdc2)-related protein kinase that plays an important role in normal cell cycle progression. Elevated expression of p58(PITSLRE) in eukaryotic cells prevents them from undergoing normal cytokinesis and appears to delay them in late telophase. To investigate the molecular mechanism of p58(PITSLRE) action, we used the yeast two-hybrid system, screened a human fetal liver cDNA library, and identified cyclin D3 as an interacting partner of p58(PITSLRE). In vitro binding assay, in vivo coimmunoprecipitation, and immunofluorescence cell staining further confirmed the association of p58(PITSLRE) with cyclin D3. This binding was observed only in the G(2)/M phase but not in the G(1)/S phase of the cell cycle; meanwhile, no interaction between p110(PITSLRE) and cyclin D3 was observed in all the cell cycle. The overexpression of cyclin D3 in 7721 cells leads to an exclusively accumulation of p58(PITSLRE) in the nuclear region, affecting its cellular distribution. Histone H1 kinase activity of p58(PITSLRE) was greatly enhanced upon interaction with cyclin D3. Furthermore, kinase activity of p58(PITSLRE) was found to increase greatly in the presence of cyclin D3 using a specific substrate, beta-1,4-galactosyltransferase 1. These data provide a new clue to our understanding of the cellular function of p58(PITSLRE) and cyclin D3.
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PMID:Interaction of p58(PITSLRE), a G2/M-specific protein kinase, with cyclin D3. 1208 95

The PITSLRE protein kinases, hereafter referred to as CDK11 because of their association with the cyclin L regulatory partner, belong to large molecular weight protein complexes that contain RNA polymerase II. These CDK11(p110) complexes have been reported to influence transcription as well as interact with the general pre-mRNA-splicing factor RNPS1. Some of these complexes may also play a role in pre-mRNA splicing. Using a two-hybrid interactive screen, the splicing protein 9G8 was identified as an in vivo partner for CDK11(p110). The identification of several splicing-related factors as CDK11(p110) interactors along with the close relationship between transcription and splicing indicated that CDK11(p110) might influence splicing activity directly. Immunodepletion of CDK11(p110) from splicing extracts greatly reduced the appearance of spliced products using an in vitro assay system. Moreover, the re-addition of these CDK11(p110) immune complexes to the CDK11(p110)-immunodepleted splicing reactions completely restored splicing activity. Similarly, the addition of purified CDK11(p110) amino-terminal domain protein was sufficient to inhibit the splicing reaction. Finally, 9G8 is a phosphoprotein in vivo and is a substrate for CDK11(p110) phosphorylation in vitro. These data are among the first demonstrations showing that a CDK activity is functionally coupled to the regulation of pre-mRNA-splicing events and further support the hypothesis that CDK11(p110) is in a signaling pathway that may help to coordinate transcription and RNA-processing events.
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PMID:CDK11 complexes promote pre-mRNA splicing. 1250 Dec 47

The serine/threonine protein kinase Akt, a downstream effector of phosphoinositide 3-kinase (PI3K), plays a pivotal role in tumorigenesis because it affects the growth and survival of cancer cells. Several laboratories have demonstrated that Akt inhibits transcriptional activation of a number of related forkhead transcription factors now referred to as FoxO1, FoxO3, and FoxO4. Akt-regulated forkhead transcription factors are involved in the control of the expression of both the cyclin-dependent kinase (cdk) inhibitor p27(Kip1) and proapoptotic Bim protein. Very little information is available concerning the importance of the PI3K/Akt pathway in HL60 human leukemia cells. Here, we present our findings showing that the PI3K/Akt axis regulates cell cycle progression of HL60 cells through multiple mechanisms also involving the control of FoxO1 and FoxO3. To this end, we took advantage of a HL60 cell clone (HL60AR cells) with a constitutively activated PI3K/Akt axis. When compared with parental (PT) HL60 cells, HL60AR cells displayed higher levels of phosphorylated FoxO1 and FoxO3. In AR cells forkhead factors localized predominantly in the cytoplasm, whereas in PT cells they were mostly nuclear. AR cells proliferated faster than PT cells and showed a lower amount of the cdk inhibitor p27(Kip1), which was mainly found in the cytoplasm and was hyperphosphorylated on threonine residues. AR cells also displayed higher levels of cyclin D1 and phosphorylated p110 Retinoblastoma protein. The protein levels of cdk2, cdk4, and cdk6 were not altered in HL60AR cells, whereas the activities of both ckd2 and cdk6 were higher in AR than in PT cells. These results show that in HL60 cells the PI3K/Akt signaling pathway may be involved in the control of the cell cycle progression most likely through mechanisms involving the activation of forkhead transcription factors.
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PMID:The phosphoinositide 3-kinase/Akt pathway regulates cell cycle progression of HL60 human leukemia cells through cytoplasmic relocalization of the cyclin-dependent kinase inhibitor p27(Kip1) and control of cyclin D1 expression. 1293 Dec 21

We report the cloning and functional characterization of human cyclin L2, a novel member of the cyclin family. Human cyclin L2 shares significant homology to cyclin L1, K, T1, T2, and C, which are involved in transcriptional regulation via phosphorylation of the C-terminal domain of RNA polymerase II. The cyclin L2 protein contains an N-terminal "cyclin box" and C-terminal dipeptide repeats of alternating arginines and serines, a hallmark of the SR family of splicing factors. A new isoform and the mouse homologue of human cyclin L2 have also been cloned in this study. Human cyclin L2 is expressed ubiquitously in normal human tissues and tumor cells. We show here that cyclin L2 co-localizes with splicing factors SC-35 and 9G8 within nuclear speckles and that it associates with hyperphosphorylated, but not hypophosphorylated, RNA polymerase II and CDK p110 PITSLRE kinase via its N-terminal cyclin domains. It can also associate with the SC-35 and 9G8 through its RS repeat region. Recombinant cyclin L2 protein can stimulate in vitro mRNA splicing. Overexpression of human cyclin L2 suppresses the growth of human hepatocellular carcinoma SMMC 7721 cells both in vitro and in vivo, inducing cellular apoptosis. This process involves up-regulation of p53 and Bax and decreased expression of Bcl-2. The data suggest that cyclin L2 represents a new member of the cyclin family, which might regulate the transcription and RNA processing of certain apoptosis-related factors, resulting in tumor cell growth inhibition and apoptosis.
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PMID:Cyclin L2, a novel RNA polymerase II-associated cyclin, is involved in pre-mRNA splicing and induces apoptosis of human hepatocellular carcinoma cells. 3259 51

Cyclin-dependent kinase 11 isoforms (CDK11) are members of the p34(cdc2) superfamily. They have been shown to play a role in RNA processing and apoptosis. In the present study, we investigate whether CDK11 interacts with 14-3-3 proteins. Our study shows that the putative 14-3-3 binding site (113-RHRSHS-118) within the N-terminal domain of CDK11(p110) is functional. Endogenous CDK11(p110) binds directly to 14-3-3 proteins and phosphorylation of the serine 118 within the RHRSHS motif seems to be required for the binding. Besides, CDK11(p110) is capable of interacting with several different isoforms of 14-3-3 proteins both in vitro and in vivo. The interaction of 14-3-3 gamma with CDK11(p110) occurs throughout the entire cell cycle and reaches maximum at the G2/M phase. Interestingly, 14-3-3 gamma shows strong interaction with N-terminal portion of caspase-cleaved CDK11(p110) (CDK11(p60)) product at 48 h after Fas treatment, which correlates with the maximal cleavage level of CDK11(p110) and the maximum activation level of CDK11 kinase activity during apoptosis. Collectively, these results suggest that CDK11 kinases could be regulated by interaction with 14-3-3 proteins during cell cycle and apoptosis.
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PMID:The cyclin-dependent kinase 11 interacts with 14-3-3 proteins. 1588 43

Previous experiments with peptide fusion proteins suggested that cyclin A/Cdk1 and Cdk2 might exhibit similar yet distinct phosphorylation specificities. Using a physiological substrate, CDP/Cux, our study confirms this notion. Proteolytic processing of CDP/Cux by cathepsin L generates the CDP/Cux p110 isoform at the beginning of S phase. CDP/Cux p110 makes stable interactions with DNA during S phase but is inhibited in G2 following the phosphorylation of serine 1237 by cyclin A/Cdk1. In this study, we propose that differential phosphorylation by cyclin A/Cdk1 and cyclin A/Cdk2 enables CDP/Cux p110 to exert its function as a transcriptional regulator specifically during S phase. We found that like cyclin A/Cdk1, cyclin A/Cdk2 interacted efficiently with recombinant CDP/Cux proteins that contain the Cut homeodomain and an adjacent cyclin-binding motif (Cy). In contrast to cyclin A/Cdk1, however, cyclin A/Cdk2 did not efficiently phosphorylate CDP/Cux p110 on serine 1237 and did not inhibit its DNA binding activity in vitro. Accordingly, co-expression with cyclin A/Cdk2 in cells did not inhibit the DNA binding and transcriptional activities of CDP/Cux p110. To confirm that the sequence surrounding serine 1237 was responsible for the differential regulation by Cdk1 and Cdk2, we replaced 4 amino acids flanking the phosphorylation site to mimic a known Cdk2 phosphorylation site present in the Cdc6 protein. Both cyclin A/Cdk2 and Cdk1 efficiently phosphorylated the CDP/Cux(Cdc6) mutant and inhibited its DNA binding activity. Altogether our results help explain why the DNA binding activity of CDP/Cux p110 is maximal during S phase and decreases in G2 phase.
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PMID:Differential regulation of CDP/Cux p110 by cyclin A/Cdk2 and cyclin A/Cdk1. 1608 23