Noncatalytic requirement for cyclin A-cdk2 in p27 turnover.
Mol Cell Biol
; 24(13): 6058-66, 2004 Jul.
Article
em En
| MEDLINE
| ID: mdl-15199159
ABSTRACT
Ubiquitin-dependent proteolysis makes a major contribution to decreasing the levels of p27. Ubiquitin-dependent proteolysis of p27(kip1) is growth and cell cycle regulated in two ways first, skp2, a component of the E3-ubiquitin ligase, is growth regulated, and second, a kinase must phosphorylate the threonine-187 position on p27 so that it can be recognized by skp2. In vitro, p27 is phosphorylated by cyclin E- and cyclin A-associated cdk2 as well as by cyclin B1-cdk1. Having analyzed the effect of different cyclin-cyclin-dependent kinase complexes on ubiquitination of p27 in a reconstitution assay system, we now report a noncatalytic requirement for cyclin A-cdk2. Multiparameter flow cytometric analysis also indicates that p27 turnover correlates best with the onset of S phase, once the levels of cyclin A become nearly maximal. Finally, increasing the amount of both cyclin E-cdk2 and skp2 was less efficient at promoting p27 ubiquitination than was increasing the amount of cyclin A-cdk2 alone in extracts prepared from cultures of >93%-purified G(1) cells. Together these lines of evidence suggest that cyclin A-cdk2 plays an ancillary noncatalytic role in the ubiquitination of p27 by the SCF(skp2) complex.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas de Ciclo Celular
/
Ciclina A
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Proteínas Supressoras de Tumor
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Quinases relacionadas a CDC2 e CDC28
Limite:
Humans
Idioma:
En
Ano de publicação:
2004
Tipo de documento:
Article