Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ribonucleotide reductase is responsible for supplying the deoxyribonucleotides required for DNA synthesis and repair. The active enzyme consists of two dissimilar protein components called R1 and R2. Immunoprecipitation of R1 and R2 proteins from [32P]orthophosphate-labeled exponentially growing mouse L cells showed that the R2 protein but not the R1 protein of ribonucleotide reductase could be phosphorylated in vivo. Two-dimensional phosphopeptide mapping experiments of trypsin-digested R2 protein showed a major spot containing more than 90% of the total radioactivity and a minor spot with the remaining radioactivity. Phosphoamino acid analysis of R2 phosphorylated protein indicated that phosphorylation occurred exclusively on serine. Protein kinase C, cAMP-dependent protein kinase, p34cdc2, and CDK2 were capable of phosphorylating the R2 protein in vitro, whereas casein kinase II was not. To determine whether any of these enzymes could phosphorylate peptides observed to be phosphorylated in actively growing cells, tryptic phosphopeptide maps of R2 that had been phosphorylated in vitro were compared with maps of R2 that had been isolated from [32P]-labeled cells. Only the phosphopeptide maps obtained with p34cdc2 and CDK2 matched the pattern found in [32P]-labeled cells. Experiments in which tryptic digests from different samples were mixed prior to two-dimensional separation demonstrated comigration of phosphopeptides obtained by in vivo phosphorylation with phosphopeptides derived from p34cdc2 or CDK2 obtained by in vitro phosphorylations. These studies indicate that protein R2 phosphorylation may play an important role in the regulation of ribonucleotide reduction, DNA synthesis, and cell cycle progression, and suggest a potentially important p34cdc2 and/or CDK2 regulation point in DNA replication.
...
PMID:Phosphorylation of ribonucleotide reductase R2 protein: in vivo and in vitro evidence of a role for p34cdc2 and CDK2 protein kinases. 825 5

The major events of the cell division cycle are triggered by periodic changes in the activity of cyclin-dependent protein kinases (CDKs). In mammals, the members of the CDK family include CDK2 and CDC2, which are thought to be involved in the control of DNA replication and mitosis, respectively. The protein kinase activity of these enzymes is controlled by a complex array of mechanisms. Activation of the CDK catalytic subunit requires association with a positive regulatory subunit (cyclin) and phosphorylation (at Thr 160 in CDK2). This activated complex can be inhibited by additional phosphorylation at Thr 14 and Tyr 15. Here we report the identification of a new mechanism for the regulation of CDK2 activity. We find that CDK2/cyclin complexes in mouse fibroblasts associate tightly with a 20K protein (CAP20). Complexes containing CAP20 were isolated from cell lysates and found to have negligible kinase activity, indicating that CAP20 association in vivo may inhibit CDK2 activity. We purified CAP20 from 3T3 cells and found that low concentrations of the protein completely inhibit the kinase activity of CDK2 in vitro. Thus CAP20 represents a new negative regulatory subunit that inhibits the activity of CDK2/cyclin complexes in mammalian cells.
...
PMID:Inhibition of CDK2 activity in vivo by an associated 20K regulatory subunit. 825 7

Deregulated expression of cyclin D1 is a feature of several neoplastic and proliferative disorders, but its normal role in the cell cycle remains unclear. Here we show that in a squamous carcinoma cell line with 11-fold amplification of the CCND1 gene, cyclin D1 associates specifically with p33cdk4 (PSK-J3) and p38cdk6 (PLSTIRE), two closely related members of the cyclin-dependent kinase (CDK) family. In these tumour cells, there is little evidence for an association between cyclin D1 and other CDKs, but in diploid human fibroblasts both CDK2 and CDK5 can be co-precipitated with cyclin D1, as well as CDK4. The data suggest that D-type cyclins participate in multiple interactions with CDKs but that the nature or stoichiometry of these associations may differ in different types of cell.
...
PMID:CDK6 (PLSTIRE) and CDK4 (PSK-J3) are a distinct subset of the cyclin-dependent kinases that associate with cyclin D1. 830 5

To understand better growth regulation in the protozoan parasite, Entamoeba histolytica (Eh), a homologue of the cdc2 gene encoding the yeast cyclin-dependent protein kinase, p34cdc2, has been cloned and sequenced. This gene, called Eh cdc2, contains a 79-bp intron located in the same place as the second of four introns in the Schizosaccharomyces pombe cdc2 gene. The sequence of an Eh cdc2 cDNA confirms the conserved eukaryotic splice donor (GT) and acceptor (AG) sites and shows that Eh is able to splice mRNAs. The spliced Eh cdc2 open reading frame is 291 amino acids (aa) long, encoding an M(r) 33,806 protein. The primary sequence of Eh cdc2 is most like those of cdc2 homologues Eg1 of Xenopus laevis and CDK2 of man (52% aa identity with each) and codes for (i) the serine (Ser), threonine (Thr), and tyrosine residues phosphorylated in p34cdc2 proteins, (ii) 32 of 33 aa conserved in other Ser/Thr protein kinases, and (iii) the sequence PVTSVRE instead of PSTAIRE found in most p34cdc2 proteins. This is the first cell-division-cycle regulatory protein homologue, as well as the first intron identified from Eh.
...
PMID:Cloning of the Eh cdc2 gene from Entamoeba histolytica encoding a protein kinase p34cdc2 homologue. 850 Jul 62

Expression of viral oncoproteins results in the loss of cell cycle checkpoint control and the accumulation of chromosomal abnormalities. Expression of both human papillomavirus type 16 oncoproteins, E6 and E7, in normal human fibroblasts completely dissociates p21 and proliferating cell nuclear antigen from the quarternary cyclin-cyclin-dependent kinase (CDK) complexes present in normal cells, causes disruption of the cyclin D-CDK4 complex and replacement with a CDK4-p16 complex, and leaves binary complexes of cyclin B1-CDC2 and cyclin A-CDK2 intact. These results are identical to those observed in fully transformed cells. The expression of the individual oncoproteins dramatically affects the association of proliferating cell nuclear antigen into the complexes while leaving the total cellular levels unaltered. Expression of low-risk human papillomavirus has no effect on cyclin complexes. These findings provide evidence for the gross alteration of cyclin-CDK complexes in preneoplastic cells and links this alteration to the loss of genomic stability.
...
PMID:Alteration of cell cycle kinase complexes in human papillomavirus E6- and E7-expressing fibroblasts precedes neoplastic transformation. 855 41

The cyclin-dependent kinases (CDKs) are among the most highly regulated enzymes in the protein-kinase family. The crystal structures of cyclin A and the CDK2-cyclin A complex spectacularly reveal the atomic basis for regulation of these enzymes and provide a template for understanding the function and regulation of other members of the CDK family.
...
PMID:Bound to activate: conformational consequences of cyclin binding to CDK2. 859 Oct 24

In many cell types, position in the cell cycle appears to play a role in determining susceptibility to apoptosis (programmed cell death), and expression of various cyclins and activation of cyclin-dependent kinases (CDKs) have been shown to correlate with the onset of apoptosis in a number of experimental systems. To assess the role of CDK-mediated cell cycle events in apoptosis, we have expressed CDK dominant negative mutants in human HeLa cells. Dominant negative mutants of CDC2, CDK2, and CDK3 each suppressed apoptosis induced by both staurosporine and tumor necrosis factor alpha, whereas a dominant negative mutant of CDK5 was without effect. Like CDC2 and CDK2, CDK3 was shown to form a complex with cyclin A in vivo. CDK5 did not bind cyclin A to any detectable extent. Overexpression of wild type CDC2, CDK2, CDK3, or cyclin A (but not cyclin B) markedly elevated the incidence of apoptosis in BCL-2+ cells, which otherwise fail to respond to these agents. These results help identify cell cycle events that are also important for efficient apoptosis.
...
PMID:Suppression of apoptosis by dominant negative mutants of cyclin-dependent protein kinases. 862 84

p107 is a retinoblastoma protein-related phosphoprotein that, when overproduced, displays a growth inhibitory function. It interacts with and modulates the activity of the transcription factor, E2F-4. In addition, p107 physically associates with cyclin E-CDK2 and cyclin A-CDK2 complexes in late G1 and at G1/S, respectively, an indication that cyclin-dependent kinase complexes may regulate, contribute to, and/or benefit from p107 function during the cell cycle. Our results show that p107 phosphorylation begins in mid G1 and proceeds through late G1 and S and that cyclin D-associated kinase(s) contributes to this process. In addition, E2F-4 binds selectively to hypophosphorylated p107, and G1 cyclin-dependent p107 phosphorylation leads to the dissociation of p107-E2F-4 complexes as well as inactivation of p107 G1 blocking function.
...
PMID:Regulation of the retinoblastoma protein-related protein p107 by G1 cyclin-associated kinases. 864 55

Cyclin-dependent kinase 2 is a serine/threonine protein kinase essential for progression of the mammalian cell cycle from G1 to S phase. CDK2 mRNA has been shown to be induced by serum in several cultured cell types. Therefore, we set out to identify elements that regulate the transcription of the human CDK2 gene and to characterize its structure. This paper describes the cloning of approximately 2.4-kilobase pair genomic DNA fragment from the upstream region of the human CDK2 gene. This fragment contains five transcription initiation sites within a 72-nucleotide stretch. A 200-base pair sub-fragment that confers 70% of maximal basal promoter activity was shown to contain two synergistically acting Sp1 sites. However, a much larger DNA fragment containing approximately 1.7 kilobase pairs of upstream sequence is required for induction of promoter activity following serum stimulation. The intron exon boundaries of seven exons in this gene were also identified, and this information will be useful for analyzing genomic abnormalities associated with CDK2.
...
PMID:Characterization of the human cyclin-dependent kinase 2 gene. Promoter analysis and gene structure. 864 14

The protein kinase inhibitor staurosporine has been shown to induce G1 phase arrest in normal cells but not in most transformed cells. Staurosporine did not induce G1 phase arrest in the bladder carcinoma cell line 5637 that lacks a functional retinoblastoma protein (pRB-). However, when infected with a pRB-expressing retrovirus [Goodrich, D. W., Chen, Y., Scully, P. & Lee, W.-H. (1992) Cancer Res. 52, 1968-1973], these cells, now pRB+, were arrested by staurosporine in G1 phase. This arrest was accompanied by the accumulation of hypophosphorylated pRB. In both the pRB+ and pRB- cells, cyclin D1-associated kinase activities were reduced on staurosporine treatment. In contrast, cyclin-dependent kinase (CDK) 2 and cyclin E/CDK2 activities were inhibited only in pRB+ cells. Staurosporine treatment did not cause reductions in the protein levels of CDK4, cyclin D1, CDK2, or cyclin E. The CDK inhibitor proteins p21(Waf1/Cip1) and p27 (Kip1) levels increased in staurosporine-treated cells. Immunoprecipitation of CDK2, cyclin E, and p2l from staurosporine-treated pRB+ cells revealed a 2.5- to 3-fold higher ratio of p2l bound to CDK2 compared with staurosporine-treated pRB- cells. In pRB+ cells, p2l was preferentially associated with Thrl6O phosphorylated active CDK2. In pRB- cells, however, p2l was bound preferentially to the unphosphorylated, inactive form of CDK2 even though the phosphorylated form was abundant. This is the first evidence suggesting that G1 arrest by 4 nM staurosporine is dependent on a functional pRB protein. Cell cycle arrest at the pRB- dependent checkpoint may prevent activation of cyclin E/CDK2 by stabilizing its interaction with inhibitor proteins p2l and p27.
...
PMID:G1 arrest and down-regulation of cyclin E/cyclin-dependent kinase 2 by the protein kinase inhibitor staurosporine are dependent on the retinoblastoma protein in the bladder carcinoma cell line 5637. 865 Jan 98


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---