Probable chromatin remodeling factor. Required for the initial establishment of DNA methylation and for accumulation of 24-nt siRNAs. May act on RNA templates by remodeling ribonucleoprotein structures and thereby influencing the availability of the RNA to polymerases. Interacts with NRPD1, NRPD3 and SHH1. In the nucleolus, localized in a ring around the inner periphery. Decreased, but not completely blocked de novo methylation. Probably due to a partial redundancy with CLSY2. Associates in vivo with Pol IV but not with Pol V. Belongs to the helicase family.