100-300bp chromatin fragments were obtained after sonication with indicated condition. Immunoprecipitated DNA-ISL1 complexes were captured by Isl1 antibody (Abcam, USA)-beads complex.Immunoprecipitated DNAs were obtained by extraction with phenol chloroform after incubated on metal bath under the condition of 65 ℃ over night. Libraries were prepared according to Illumina's instructions accompanying the DNA Sample Kit.