Spreading the silence.

RITS (RNA-induced initiation of transcriptional gene silencing complex) plays diverse roles in heterochromatin regulation: silencing transcription by recruitment of chromatin modifiers and destroying transcripts by RNAi. In a recent issue of Molecular Cell, Li et al. now show that the polymerization of Tas3, a component of RITS, contributes to the spreading of silencing mediated by RITS.