Figure 4.

HP1-dependent recruitment of BRCA1 to DSB sites. AsiSI-ER-U2OS cells and HP1-depleted AsiSI-ER-U2OS cells were cultured and treated with 4-OHT (4-hydroxytamoxifen; 100 µM) for 4 h. Soluble chromatins were prepared from each culture and immunoprecipitated with specific antibodies (A: BRCA1, B: 53BP1, C: Rad51 and D: HP1). Immunoprecipitated chromatins were analyzed by quantitative PCR using specific primer pairs located at Chr 1: chr1_89231183, Chr 6: chr6_90404906, Chr 21: distal region of chr21_21292316. The results shown are relative signals from the individual precipitated DNA compared with input chromatin. siHP1 is siHP1 α, β and γ combined. Figure 4B includes two insets with enlarged scales showing the increased 53BP1 occupancy at DSB sites of Chr 1 and Chr 6 on 4-OHT treatment.