Laboratory for Developmental Genomics, RIKEN Center for Developmental Biology, Kobe, Hyogo, 650-0047 Japan.
J Cell Biol. 2011 Mar 21;192(6):929-37. doi: 10.1083/jcb.201010106. Epub 2011 Mar 14.
Germ granules are germ lineage-specific ribonucleoprotein (RNP) complexes, but how they are assembled and specifically segregated to germ lineage cells remains unclear. Here, we show that the PGL proteins PGL-1 and PGL-3 serve as the scaffold for germ granule formation in Caenorhabditis elegans. Using cultured mammalian cells, we found that PGL proteins have the ability to self-associate and recruit RNPs. Depletion of PGL proteins from early C. elegans embryos caused dispersal of other germ granule components in the cytoplasm, suggesting that PGL proteins are essential for the architecture of germ granules. Using a structure-function analysis in vivo, we found that two functional domains of PGL proteins contribute to germ granule assembly: an RGG box for recruiting RNA and RNA-binding proteins and a self-association domain for formation of globular granules. We propose that self-association of scaffold proteins that can bind to RNPs is a general mechanism by which large RNP granules are formed.
生殖质是生殖系特异性的核糖核蛋白 (RNP) 复合物，但它们如何组装并特异性地分配到生殖系细胞中尚不清楚。在这里，我们显示 PGL 蛋白 PGL-1 和 PGL-3 可作为秀丽隐杆线虫生殖质形成的支架。使用培养的哺乳动物细胞，我们发现 PGL 蛋白具有自我缔合和招募 RNP 的能力。从早期秀丽隐杆线虫胚胎中耗尽 PGL 蛋白会导致其他生殖质成分在细胞质中分散，表明 PGL 蛋白对于生殖质的结构是必不可少的。通过体内的结构功能分析，我们发现 PGL 蛋白的两个功能域有助于生殖质的组装：一个用于招募 RNA 和 RNA 结合蛋白的 RGG 盒，以及一个用于形成球形颗粒的自我缔合结构域。我们提出，能够结合 RNP 的支架蛋白的自我缔合是形成大型 RNP 颗粒的通用机制。
