PDF(Pubmed)
Abstract：
RNA-binding proteins FBF-1 and FBF-2 (FBFs) are required for germline stem cell maintenance and the sperm/oocyte switch in Caenorhabditis elegans, although the mechanisms controlling FBF protein levels remain unknown. We identified an interaction between both FBFs and CSN-5), a component of the constitutive photomorphogenesis 9 (COP9) signalosome best known for its role in regulating protein degradation. Here, we find that the Mpr1/Pad1 N-terminal metalloprotease domain of CSN-5 interacts with the Pumilio and FBF RNA-binding domain of FBFs and the interaction is conserved for human homologs CSN5 and PUM1. The interaction between FBF-2 and CSN-5 can be detected in vivo by proximity ligation. csn-5 mutation results in the destabilization of FBF proteins, which may explain previously observed decrease in the numbers of germline stem and progenitor cells, and disruption of oogenesis. The loss of csn-5 does not decrease the levels of a related PUF protein PUF-3, and csn-5(lf) phenotype is not enhanced by fbf-1/2 knockdown, suggesting that the effect is specific to FBFs. The effect of csn-5 on oogenesis is largely independent of the COP9 signalosome and is cell autonomous. Surprisingly, the regulation of FBF protein levels involves a combination of COP9-dependent and COP9-independent mechanisms differentially affecting FBF-1 and FBF-2. This work supports a previously unappreciated role for CSN-5 in the stabilization of germline stem cell regulatory proteins FBF-1 and FBF-2.
摘要：
RNA结合蛋白FBF-1和FBF-2（FBF）是秀丽隐杆线虫生殖系干细胞维持和精子/卵母细胞转换所必需的，尽管控制FBF蛋白水平的机制仍然未知。我们确定了FBF和CSN-5之间的相互作用，CSN-5是COP9（组成型光形态发生9）的组成部分，以其在调节蛋白质降解中的作用而闻名。这里,我们发现CSN-5的Mpr1/Pad1N端金属蛋白酶域与FBF的Pumilio和FBFRNA结合域相互作用，并且这种相互作用对于人类同源物CSN5和PUM1是保守的。FBF-2和CSN-5之间的相互作用可以通过邻近连接在体内检测。csn-5突变导致FBF蛋白不稳定，这可以解释以前观察到的生殖干细胞和祖细胞数量的减少，和卵子发生的破坏。csn-5的丢失不会降低相关PUF蛋白PUF-3的水平，并且csn-5（lf）表型不会通过fbf-1/2敲低而增强，这表明这种效应是FBF特有的。csn-5对卵子发生的影响在很大程度上与COP9信号体无关，并且是细胞自主的。令人惊讶的是,FBF蛋白水平的调节涉及不同影响FBF-1和FBF-2的COP9依赖性和非依赖性机制的组合。这项工作支持CSN-5在种系干细胞调节蛋白FBF-1和FBF-2的稳定中先前未被重视的作用。
