Wang W, Chevray P M, Nathans D
Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Proc Natl Acad Sci U S A. 1996 Aug 6;93(16):8236-40. doi: 10.1073/pnas.93.16.8236.
In a search for regulatory proteins that interact with the leucine zipper motif of c-Fos in the yeast two-hybrid screen, we have identified a protein (FZA-B) that has extensive sequence similarity to SUG1 of Saccharomyces cerevisiae. Here we show that FZA-B can functionally substitute for SUG1 in yeast and that FZA-B interacts with Fos proteins in vitro through their leucine zippers. In rat liver and in HeLa cells, FZA-B is present in the 26S proteasome complex, as is c-Fos. Immobilized antibody raised against an FZA-B-specific peptide depleted peptidase activity, proteasomal proteins, FZA-B, and c-Fos from a 26S proteasome preparation. FZA-B is found predominantly in the nuclear fraction of COS cells expressing an FZA-B transgene and in the nuclear 26S proteasome of HeLa cells. We conclude that FZA-B is the mammalian homolog of SUG1 (mSug1) and that it is present in the nuclear 26S proteasome of cells. Our results suggest that mSug1 may be involved in the degradation of c-Fos and other transcription factors.
在酵母双杂交筛选中寻找与c-Fos亮氨酸拉链基序相互作用的调节蛋白时，我们鉴定出一种与酿酒酵母SUG1具有广泛序列相似性的蛋白（FZA-B）。在此我们表明，FZA-B在酵母中可功能性替代SUG1，并且FZA-B在体外通过其亮氨酸拉链与Fos蛋白相互作用。在大鼠肝脏和HeLa细胞中，FZA-B与c-Fos一样存在于26S蛋白酶体复合物中。针对FZA-B特异性肽产生的固定化抗体从26S蛋白酶体制剂中去除了肽酶活性、蛋白酶体蛋白、FZA-B和c-Fos。FZA-B主要存在于表达FZA-B转基因的COS细胞的核部分以及HeLa细胞的核26S蛋白酶体中。我们得出结论，FZA-B是SUG1的哺乳动物同源物（mSug1），并且它存在于细胞的核26S蛋白酶体中。我们的结果表明，mSug1可能参与c-Fos和其他转录因子的降解。
