PDF(Pubmed)
Abstract：
The piRNA pathway is a conserved germline-specific small RNA pathway that ensures genomic integrity and continued fertility. In C. elegans and other nematodes, Type-I piRNAs are expressed from >10,000 independently transcribed genes clustered within two discrete domains of 1.5 and 3.5 MB on Chromosome IV. Clustering of piRNA genes contributes to their germline-specific expression, but the underlying mechanisms are unclear. We analyze isolated germ nuclei to demonstrate that the piRNA genomic domains are located in a heterochromatin-like environment. USTC (Upstream Sequence Transcription Complex) promotes strong association of nucleosomes throughout piRNA clusters, yet organizes the local nucleosome environment to direct the exposure of individual piRNA genes. Localization of USTC to the piRNA domains depends upon the ATPase chromatin remodeler ISW-1, which maintains high nucleosome density across piRNA clusters and ongoing production of piRNA precursors. Overall, this work provides insight into how chromatin states coordinate transcriptional regulation over large genomic domains, with implications for global genome organization.
摘要：
piRNA途径是保守的种系特异性小RNA途径,其确保基因组完整性和持续的生育力。在秀丽隐杆线虫和其他线虫中，I型piRNA从在染色体IV上的1.5和3.5MB的两个离散结构域内聚集的>10,000个独立转录的基因表达。piRNA基因的聚类有助于它们的种系特异性表达，但潜在的机制尚不清楚。我们分析了分离的胚核，以证明piRNA基因组结构域位于异染色质样环境中。USTC（上游序列转录复合物）促进整个piRNA簇的核小体的强关联，然而，组织局部核小体环境来指导个体piRNA基因的暴露。USTC对piRNA结构域的定位取决于ATP酶染色质重塑剂ISW-1,其维持跨piRNA簇的高核小体密度和piRNA前体的持续产生。总的来说,这项工作提供了深入了解染色质状态如何协调大基因组域的转录调控，对全球基因组组织的影响。
