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 origin recognition complex (ORC) is involved in formation of prereplicative complexes (pre-RCs) on replication origins in the G1 phase. At the G1/S transition, elevated cyclin E-CDK2 activity triggers 1DNA replication to enter S phase. The CDK cycle works as an engine that drives progression of cell cycle events by successive activation of different types of cyclin-CDK. However, how the CDK cycle is coordinated with replication initiation remains elusive. Here we report that acute depletion of ORC2 by RNA interference (RNAi) arrests cells with low cyclin E-CDK2 activity. This result suggests that loss of a replication initiation protein prevents progression of the CDK cycle in G1. p27 and p21 proteins accumulate following ORC2 RNAi and are required for the CDK2 inhibition. Restoration of CDK activity by co-depletion of p27 and p21 allows many ORC2-depleted cells to enter S phase and go on to mitosis. However, in some cells the release of the CDK2 block caused catastrophic events like apoptosis. Therefore, the CDK2 inhibition observed following ORC2 RNAi seems to protect cells from premature S phase entry and crisis in DNA replication. These results demonstrate an unexpected role of ORC2 in CDK2 activation, a linkage that could be important for maintaining genomic stability.
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PMID:Acute reduction of an origin recognition complex (ORC) subunit in human cells reveals a requirement of ORC for Cdk2 activation. 1594 61

The origin-recognition complex (ORC) has an essential role in defining DNA replication origins and in chromosome segregation. Recent studies in Drosophila orc2 mutants, and in human cells depleted of ORC2, have suggested that this factor is also implicated in mitotic chromosome assembly. We asked whether ORC was required for M phase chromosome assembly independently of its function in DNA replication. We performed depletion assays and reconstitution experiments in Xenopus egg extracts, in conditions of M phase chromosome assembly coupled or uncoupled from DNA replication. We show that, although ORC is dispensable for mitotic chromosome condensation, it is necessary at the interphase-mitosis transition for proper mitotic chromosome assembly to occur in a reaction not strictly dependent on DNA replication. This function involves the recruitment to chromatin of cdc2 kinase and the chromatin disassembly of interphasic replication protein A (RPA) foci. Furthermore, we show that mutations of RPA at the cdc2 kinase site prevents RPA dissociation from chromatin and impairs mitotic chromosome assembly without affecting DNA replication. Our results support the conclusion that in addition to its role in the assembly of prereplication complexes (pre-RCs), at the G1-S transition, ORC is also required for their disassembly at mitotic entry.
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PMID:ORC is necessary at the interphase-to-mitosis transition to recruit cdc2 kinase and disassemble RPA foci. 1652 48

Using real-time RT-PCR and Western blot analysis in bovine kidney epithelial cells, we systematically investigated the effects of butyrate on patterns of gene expression relevant to DNA replication apparatus. The real-time PCR and Western blot data generally confirmed previously reported microarray data. Of the five genes tested by quantitative RT-PCR, CDKN1A (p21(waf1)) was up regulated, CDC2/cdk1, MCM6, ORC1L were down regulated, while ORC3L expression remained unchanged following butyrate treatment. Also consistent with RT-PCR results, Western blot analysis confirmed that butyrate up-regulated cyclin-kinase inhibitor p21(waf1) in a does-dependent manner. In contrast, butyrate treatment had no effect on the expression of ERK 1/2 proteins. Also consistent with mRNA results, ORC1 and MCM3 proteins were down-regulated by butyrate treatment, while ORC2 protein remained unchanged. The present results suggest that ORC1, not ORC2 or ORC3, along with MCM proteins play a critical role in regulating the initiation of DNA replication and cell cycle progression in MDBK cells and are targets of butyrate regulation.
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PMID:Butyrate induced cell cycle arrest in bovine cells through targeting gene expression relevant to DNA replication apparatus. 1978 80