CELL-CYCLE REGULATION OF B-MYB PROTEIN EXPRESSION - SPECIFIC PHOSPHORYLATION DURING THE S-PHASE OF THE CELL-CYCLE

Citation
C. Robinson et al., CELL-CYCLE REGULATION OF B-MYB PROTEIN EXPRESSION - SPECIFIC PHOSPHORYLATION DURING THE S-PHASE OF THE CELL-CYCLE, Oncogene, 12(9), 1996, pp. 1855-1864
Citations number
32
Categorie Soggetti
Oncology,Biology,"Cell Biology
Journal title
ISSN journal
09509232
Volume
12
Issue
9
Year of publication
1996
Pages
1855 - 1864
Database
ISI
SICI code
0950-9232(1996)12:9<1855:CROBPE>2.0.ZU;2-L
Abstract
Previous studies revealed that transcription of B-Myb, which encodes a transcription factor related to the c-Myb proto-oncoprotein, is cell- cycle regulated by an E2F transcription factor-mediated repression mec hanism operating in G(0)/G(1). To begin to determine the consequences of transcriptional regulation on B-Myb function, we report here furthe r studies of B-Myb protein expression in the cell cycle. We found that G(0)-arrest of serum-deprived mouse fibroblasts was achieved without significant reduction in B-Myb levels, moreover, overexpression of B-M yb in stably transfected cells did not prevent their entry into G(0). Following serum-induction of arrested fibroblasts, B-Myb abundance inc reased as cells entered S phase to levels significantly greater than f ound in cycling cells. This was accompanied by the appearance of a nov el phosphorylated form of B-Myb (112 kDa) of distinctly lower electrop horetic mobility than B-Myb present in G(1) (110 kDa). The 112 kDa spe cies was S phase-specific even in transfected cells overexpressing B-M yb. Consistent with modification in the S phase of the cell cycle, pre liminary evidence suggested that a cyclin A/cdk2, but not cyclin E/cdk 2 or cyclin D1/cdk4, complex could induce a similar electrophoretic mo bility change in baculovirus-specified B-Myb. These findings show that B-Myb expression may be subject to two levels of control during the c ell cycle, transcription and protein phosphorylation.