Microsomal localization of cyclin A and cdk2 in proliferating rat liver cells.
The expression and intracellular localization of cyclin A and cdk2 have been analyzed in rat liver cells proliferatively activated in vivo by a partial hepatectomy. Western blot analysis revealed that cyclin A started to increase during G1 (at 6 h after hepatectomy) reaching maximal levels during S phase (at 18 h). Cdk2 began to increase during late G1 (at 12 h) peaking also at 18 h. At the latter time cyclin A was mainly localized in the microsomal fraction, although it was also present in cytosol, plasma membrane and nucleus. Active cyclin/cdks complexes containing cyclin A and cdk2 were obtained by precipitation with p13-Sepharose after solubilization of microsomes with triton X-100. The presence of active cyclin A/cdk2 complexes in microsomes was confirmed by immunoprecipitation experiments with anti-cdk2 antibodies. These results suggest a putative role of cyclin A/cdk2 during S phase which would be related with microsomal function.
Castro
A
A
Departament de Biologia Cellular, Facultat de Medicina, Universitat de Barcelona, Spain.
Jaumot
M
M
Vergés
M
M
Agell
N
N
Bachs
O
O
D000818:Animals; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D016213:Cyclins / Q000378:metabolism*; D008115:Liver Regeneration; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000737:chemistry
D016213:Cyclins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases