Staged worms were washed twice with M9 buffer and freezed in liquid nitrogen. Frozan worms were crushed using a pestle and a mortar and resuspended in Chip buffer. Extracts were sonicated and precleared before ChIP experiments. Libraires were made followinf the recommended Illumina protocol for TruSeq Chip sample preparation guide (part #15023092 Rev A, August 2012).