For RNA-seq, drosophila third instar larvae wing discs from indicated genetypes were dissected into Trizol, and total RNA was extracted for the construction of sequencing libraries. For ChIP-seq, drosophila third instar larvae wing discs from Act5c-Gal4 were cross-linked, sonicated and subjected for ChIP assay with anti-H4K20me1 antibody. After reverse cross-link and protein digestion with proteinase K, the immunoprecipitated genomic DNA was extracted with DNA purification kit (QIAGEN) and for construction of sequencing libraries. ChIP-seq and unstrand RNA-seq libraries were prepared for sequencing using standard Illumina protocols.