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Mol. Cell. Biol., May 1995, 2682-2688, Vol 15, No. 5
FK Chan, J Zhang, L Cheng, DN Shapiro and A Winoto
The cell cycle in mammalian cells is regulated by a series of cyclins and
cyclin-dependent kinases (CDKs). The G1/S checkpoint is mainly dictated by
the kinase activities of the cyclin D-CDK4 and/or cyclin D- CDK6 complex
and the cyclin E-CDK2 complex. These G1 kinases can in turn be regulated by
cell cycle inhibitors, which may cause the cells to arrest at the G1 phase.
In T-cell hybridomas, addition of anti-T- cell receptor antibody results
not only in G1 arrest but also in apoptosis. In searching for a protein(s)
which might interact with Nur77, an orphan steroid receptor required for
activation-induced apoptosis of T-cell hybridomas, we have cloned a novel
human and mouse CDK inhibitor, p19. The deduced p19 amino acid sequence
consists of four ankyrin repeats with 48% identity to p16. The human p19
gene is located on chromosome 19p13, distinct from the positions of p18,
p16, and p15. Its mRNA is expressed in all cell types examined. The p19
fusion protein can associate in vitro with CDK4 but not with CDK2, CDC2, or
cyclin A, B, E, or D1 to D3. Addition of p19 protein can lead to inhibition
of the in vitro kinase activity of cyclin D-CDK4 but not that of cyclin
E-CDK2. In T-cell hybridoma DO11.10, p19 was found in association with CDK4
and CDK6 in vivo, although its association with Nur77 is not clear at this
point. Thus, p19 is a novel CDK inhibitor which may play a role in the cell
cycle regulation of T cells.
Copyright © 1995, American Society for Microbiology
Identification of human and mouse p19, a novel CDK4 and CDK6 inhibitor with homology to p16ink4
Department of Molecular and Cell Biology, University of California, Berkeley 94720-3200, USA.
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