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Cell cycle‐dependent variations in c‐Jun and JunB phosphorylation: a role in the control of cyclin D1 expression
Author(s) -
Bakiri Latifa,
Lallemand Dominique,
BossyWetzel Ella,
Yaniv Moshe
Publication year - 2000
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/19.9.2056
Subject(s) - junb , biology , cyclin d1 , ap 1 transcription factor , transactivation , phosphorylation , microbiology and biotechnology , cell cycle , cyclin dependent kinase 1 , cyclin a , cyclin , cyclin d , transcription factor , cyclin b , genetics , cell , gene
The transcription factor AP‐1, composed of Jun and Fos proteins, is a major target of mitogen‐activated signal transduction pathways. However, little is known about AP‐1 function in normal cycling cells. Here we report that the quantity and the phosphorylation state of the c‐Jun and JunB proteins vary at the M–G 1 transition. Phosphorylation of JunB by the p34 cdc2 –cyclin B kinase is associated with lower JunB protein levels in mitotic and early G 1 cells. In contrast, c‐Jun levels remain constant while the protein undergoes N‐terminal phosphorylation, increasing its transactivation potential. Since JunB represses and c‐Jun activates the cyclin D1 promoter, these modifications of AP‐1 activity during the M–G 1 transition could provide an impetus for G 1 progression by a temporal increase in cyclin D1 transcription. These findings constitute a novel example of a reciprocal connection between transcription factors and the cell cycle machinery.