Roles of Fission Yeast Grc3 Protein in Ribosomal RNA Processing and Heterochromatic Gene Silencing
Roles of Fission Yeast Grc3 Protein in Ribosomal RNA Processing and Heterochromatic Gene Silencing
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DOI：
10.1074/jbc.m110.201343
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发表时间：
2011-04-29
影响因子：
4.8
通讯作者：
Nakayama, Jun-ichi
中科院分区：
文献类型：
--
作者：
Kitano, Erina;Hayashi, Aki;Nakayama, Jun-ichi
Grc3是一种进化保守蛋白。全基因组芽殖酵母研究表明，Grc3参与rRNA加工。在分裂酵母裂糖酵母（Schizosaccharomyces pombe）中，Grc3被确定为具有明显核点定位的因子，但其确切的生理功能尚不清楚。在这里，我们发现S. pombe Grc3是rRNA加工和异色基因沉默所必需的。细胞学分析显示，Grc3核点与异色区相对应，部分Grc3也存在于核仁外周区。消耗异色蛋白Swi6或Clr4会消除Grc3的异色定位，并导致其在核核周围区域优先积累，表明其与这些核室的动态关联。表达突变体grc3的细胞在25s rRNA成熟和异色基因沉默方面存在缺陷。通过对含有grc3复合物的蛋白分析，鉴定出Las1和IPI复合物的组成部分（Rix1、Ipi1和Crb3）。所有这些与Grc3相互作用的蛋白都表现出与Grc3相似的动态核定位，并且这些条件突变体在rRNA加工和着丝粒转录物沉默方面都表现出缺陷。我们的数据表明，Grc3与Las1和IPI复合物在核糖体生物发生和异染色质组装中协同作用。
Grc3 is an evolutionarily conserved protein. Genome-wide budding yeast studies suggest that Grc3 is involved in rRNA processing. In the fission yeast Schizosaccharomyces pombe, Grc3 was identified as a factor exhibiting distinct nuclear dot localization, yet its exact physiological function remains unknown. Here, we show that S. pombe Grc3 is required for both rRNA processing and heterochromatic gene silencing. Cytological analysis revealed that Grc3 nuclear dots correspond to heterochromatic regions and that some Grc3 is also present in the nucleolar peripheral region. Depleting the heterochromatic proteins Swi6 or Clr4 abolished heterochromatic localization of Grc3 and resulted in its preferential accumulation in the peri-nucleolar region, suggesting its dynamic association with these nuclear compartments. Cells expressing mutant grc3 showed defects in 25 S rRNA maturation and in heterochromatic gene silencing. Protein analysis of Grc3-containing complexes led to the identification of Las1 and components of the IPI complex (Rix1, Ipi1, and Crb3). All of these Grc3-interacting proteins showed a dynamic nuclear localization similar to that observed for Grc3, and those conditional mutants showed defects in both rRNA processing and silencing of centromeric transcripts. Our data suggest that Grc3 functions cooperatively with Las1 and the IPI complex in both ribosome biogenesis and heterochromatin assembly.