E1A can evoke G1 exit in cardiac myocytes and other cell types by displacing E2F transcription factors from tumor suppressor "pocket" proteins and by a less well-characterized p300-dependent pathway. Bypassing pocket proteins (through overexpression of E2F-1) reproduces the effect of inactivating pocket proteins (through E1A binding); however, pocket proteins associate with a number of molecula...

Mitosis requires cyclin-dependent kinase (cdk) 1-cyclin B activity [1]. Exit from mitosis depends on the inactivation of the complex by the degradation of cyclin B [2]. Cdk2 is also active during mitosis [3, 4]. In Xenopus egg extracts, cdk2 is primarily in complex with cyclin E, which is stable [5]. At the end of mitosis, downregulation of cdk2-cyclin E activity is accompanied by inhibitory ph...

Cisplatin is one of the most effective chemotherapeutics, but its usefulness is limited by its toxicity to normal tissues, including cells of the kidney proximal tubule. The purpose of these studies was to determine the mechanism of cisplatin cytotoxicity. It was shown in vivo that cisplatin administration induces upregulation of the gene for the p21 cyclin-dependent kinase (cdk) inhibitor in k...

The cyclin-dependent protein kinases (CDKs) are activated by association with cyclins and by phosphorylation at a conserved threonine residue by the CDK-activating kinase (CAK). We have studied the binding of various human CDK and cyclin subunits in vitro, using purified proteins derived from baculovirus-infected insect cells. We find that most CDK-cyclin complexes known to exist in human cells...

TopBP1 has important roles in both DNA replication and checkpoint regulation in vertebrates. We have identified a protein called Treslin that associates with TopBP1 in Xenopus egg extracts. Depletion of Treslin from egg extracts strongly inhibits chromosomal DNA replication. Binding of Treslin to chromatin in egg extracts occurs independently of TopBP1. However, loading of the initiator protein...

Human cytomegalovirus (HCMV) stimulates numerous cellular pathways upon infection. One of these pathways involves activation of cyclin E/Cdk2. Recent reports have demonstrated that Cdk2 is retained in the cytoplasm of cells arrested in GO by serum deprivation, sequestered from its regulatory subunit cyclin E which is located within the nucleus. Cdk2 rapidly enters the nucleus and becomes active...

Aberrant activation of cell cycle molecules has been postulated to play a role in apoptosis ("catastrophic cell cycle"). Here we show that in noncycling developing thymocytes, the cyclin- dependent kinase Cdk2 is activated in response to all specific and nonspecific apoptotic stimuli tested, including peptide-specific thymocyte apoptosis. Cdk2 was found to function upstream of the tumor suppres...

p27(Kip1), a cyclin-dependent kinase (CDK) inhibitor, is a multi-functional protein that regulates various cellular activities. Trophoblast proliferation, migration and invasion are some of the key processes of placental development. We have recently reported that Nodal, a member of the transforming growth factor-β (TGF-β) superfamily, inhibits human trophoblast cell proliferation, migration an...

E2F1 is a key regulator that links cell cycle progression and cell death. E2F1 activity is controlled by Cdk2-cyclin complexes via several mechanisms, such as phosphorylation of retinoblastoma protein (pRb) to release E2F1, direct phosphorylation, and stable physical interaction. We have demonstrated that cisplatin cytotoxicity depends on Cdk2 activity, and Cdk2 inhibition protects kidney cells...

Nek2 (NIMA-related kinase 2) is a cell cycle-dependent serine/threonine protein kinase that regulates centrosome separation at the onset of mitosis. Overexpression of Nek2 is common in human cancers and suppression can restrict tumor cell growth and promote apoptosis. Nek2 inhibition with small molecules, therefore, offers the prospect of a new therapy for cancer. To achieve this goal, a better...