Open AccessExistence of different Fos/Jun complexes during the G0-to-G1 transition and during exponential growth in mouse fibroblasts: differential role of Fos proteins.
Author(s) -
K Kovary,
Rodrigo Bravo
Publication year - 1992
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.12.11.5015
Subject(s) - junb , fosb , biology , immunoprecipitation , exponential growth , ap 1 transcription factor , microbiology and biotechnology , stimulation , transition (genetics) , c fos , biochemistry , gene expression , gene , endocrinology , mathematical analysis , mathematics
We have determined the different Fos/Jun complexes present in Swiss 3T3 cells either following serum stimulation of quiescent cells or during exponential growth by immunoprecipitation analyses. We have shown that while c-Fos is the major Fos protein associated with the Jun proteins (c-Jun, JunB, and JunD) soon after serum stimulation, at later times Fra-1 and Fra-2 are the predominant Fos proteins associated with the different Jun proteins. During exponential growth, the synthesis of Fra-1 and Fra-2 is maintained at a significant level, in contrast to c-Fos and FosB, which are expressed at very low or undetectable levels. Consequently, Fra-1 and Fra-2 are the main Fos proteins complexed with the Jun proteins in asynchronously growing cells. To determine whether the Fos proteins are differentially required during the G0-to-G1 transition and exponential growth for the entrance into S phase, we microinjected affinity-purified antibodies directed against c-Fos, FosB, Fra-1, and Fra-2. We have found that while the activities of c-Fos and FosB are required mostly during the G0-to-G1 transition, Fra-1 and Fra-2 are involved both in the G0-to-G1 transition and in asynchronous growth.