Worms were harvested from plates with 1 X PBS buffer and washed four times. The compact worm slurry (250 µl) was resuspended in 4 ml cross-linking buffer (1% formaldehyde in 1 X PBS) followed by homogenization with 7 ml glass Dounce homogenizer. A total of 5 ng of DNA was used as a starting material for library preparation according to the Illumina, Inc. ( San Diego, CA, USA) protocol, "Preparing Samples for ChIP Sequencing of DNA".