Kovary K, Bravo R
Department of Molecular Biology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey 08543-4000.
Mol Cell Biol. 1992 Nov;12(11):5015-23. doi: 10.1128/mcb.12.11.5015-5023.1992.
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.
我们通过免疫沉淀分析确定了血清刺激静止的瑞士3T3细胞后或指数生长期间细胞中存在的不同Fos/Jun复合物。我们已经表明，血清刺激后不久，c-Fos是与Jun蛋白（c-Jun、JunB和JunD）相关的主要Fos蛋白，但在随后的时间里，Fra-1和Fra-2是与不同Jun蛋白相关的主要Fos蛋白。在指数生长期间，Fra-1和Fra-2的合成维持在显著水平，而c-Fos和FosB则以非常低或无法检测到的水平表达。因此，Fra-1和Fra-2是在异步生长细胞中与Jun蛋白复合的主要Fos蛋白。为了确定在从G0期到G1期的转变以及指数生长期间进入S期是否对Fos蛋白有不同的需求，我们显微注射了针对c-Fos、FosB、Fra-1和Fra-2的亲和纯化抗体。我们发现，虽然c-Fos和FosB的活性主要在从G0期到G1期的转变期间是必需的，但Fra-1和Fra-2既参与从G0期到G1期的转变，也参与异步生长。
