BACKGROUND Cyclin E is the normal inducer of S phase in G1 cells of Drosophila embryos. Stable G1 quiescence requires the downregulation both of cyclin E and of other factors that can bypass the normal regulation of cell cycle progression. RESULTS High-level expression of cyclin A triggered the G1/S transition in wild-type embryos and in mutant embryos lacking cyclin E. Three types of control...

Cell cycle deregulation and genomic instability play a major role in the aberrant cell proliferation that characterizes tumorigenesis. A novel role of the cyclin e isoform cyclin e2 in these processes is reported in the manuscript " Cyclin e2 induces genomic instability by mechanisms distinct from cyclin e1 " by Caldon et al. 1 in another issue of Cell Cycle, evidence that regulation of cyclin ...

Cell cycle deregulation and genomic instability play a major role in the aberrant cell proliferation that characterizes tumorigenesis. A novel role of the cyclin e isoform cyclin e2 in these processes is reported in the manuscript " Cyclin e2 induces genomic instability by mechanisms distinct from cyclin e1 " by Caldon et al. 1 in another issue of Cell Cycle, evidence that regulation of cyclin ...

D-type cyclins (cyclins D1, D2, and D3) promote G1-S progression and are aberrantly expressed in cancer. We reported previously that all-trans-retinoic acid chemo-prevented carcinogenic transformation of human bronchial epithelial (HBE) cells through proteasomal degradation of cyclin D1. Retinoic acid is shown here to activate distinct mechanisms to regulate different D-type cyclins in HBE cell...

Cyclins are regulatory subunits of cyclin-dependent kinases. Cyclin A, the first cyclin ever cloned, is thought to be an essential component of the cell-cycle engine. Mammalian cells encode two A-type cyclins, testis-specific cyclin A1 and ubiquitously expressed cyclin A2. Here, we tested the requirement for cyclin A function using conditional knockout mice lacking both A-type cyclins. We found...

Cyclin G1 was identified as a transcriptional target of p53 that encodes a protein with strong homology to the cyclin family of cell cycle regulators. We show that either ectopically expressed or endogenous cyclin G1 protein is very unstable, undergoes modification with ubiquitin, and is likely degraded by the proteasome. Ectopic cyclin G1 protein stability is increased by cyclin box mutation o...

Recent studies suggest that cyclin D1 mediates progression of hepatocytes through G1 phase of the cell cycle. The present study further examines the regulation of cyclin D1-dependent kinase activity and the interplay between cyclin D1 and other G1phase regulatory proteins during liver regeneration. After 70% partial hepatectomy in rats, there was upregulation of kinase activity associated with ...

Cyclin-dependent kinases are most extensively studied targets for cancer chemotherapy since the tumor cells exhibit false checkpoints and can proliferate even if the genome is compromised. Cyclin-dependent kinases ensure the tight regulation of the cell cycle execution by mediating phosphorylation of cellular proteins. Deregulation of the cyclin-dependent kinase 2 activity by cellular and exter...

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