A chromodomain protein mediates heterochromatin-directed piRNA expression
Xinya Huang, Peng Cheng, Chenchun Weng, Zongxiu Xu, Chenming Zeng, Zheng Xu, Xiangyang Chen, Chengming Zhu, Shouhong Guang, Xuezhu Feng
Abstract
, transcription of piRNA clusters depends on the chromatin microenvironment and a chromodomain-containing protein, UAD-2. piRNA clusters form distinct focus in germline nuclei. We conducted a forward genetic screening and identified UAD-2 that is required for piRNA focus formation. In the absence of histone 3 lysine 27 methylation or proper chromatin-remodeling status, UAD-2 is depleted from the piRNA focus. UAD-2 recruits the upstream sequence transcription complex (USTC), which binds the Ruby motif to piRNA promoters and promotes piRNA generation. Vice versa, the USTC complex is required for UAD-2 to associate with the piRNA focus. Thus, transcription of heterochromatic small RNA source loci relies on coordinated recruitment of both the readers of histone marks and the core transcriptional machinery to DNA.