RNA interference (RNAi) is critical for the assembly of heterochromatin at 
Schizosaccharomyces pombe centromeres. Central to this process is the 
RNA-induced initiation of transcriptional gene silencing (RITS) complex, which 
physically anchors small noncoding RNAs to chromatin. RITS includes Ago1, the 
chromodomain protein Chp1, and Tas3, which forms a bridge between Chp1 and Ago1. 
Chp1 is a large protein with no recognizable domains, apart from its 
chromodomain. Here we describe how the structured C-terminal half of Chp1 binds 
the Tas3 N-terminal domain, revealing the tight association of Chp1 and Tas3. 
The structure also shows a PIN domain at the C-terminal tip of Chp1 that 
controls subtelomeric transcripts through a post-transcriptional mechanism. We 
suggest that the Chp1-Tas3 complex provides a solid and versatile platform to 
recruit both RNAi-dependent and RNAi-independent gene-silencing pathways for 
locus-specific regulation of heterochromatin.