Mapping of CTCF occupancy in interphase and mitosis cells

To address whether CTCF is involved in the transcription of early G1 genes immediately after mitotic exit, we carried out ChIP sequencing (ChIP-seq) experiments to evaluate CTCF binding to genomic DNA in asynchronous cells and nocodazole-arrested mitotic cells. Of the 62,996 peaks identified in the asynchronous cells, 41,397 peaks (65.71%) were lost in the mitotic cells. However, the 21,599 peaks (34.29%) were identified in the both conditions, indicating that the enrichment level of CTCF is decreased in the mitotic cells. It has been reported that expression profiles of the first 2 hours of G1 phase in HeLa cells. A scatter plot comparison of the genes expressed in the early G1 phase indicated the reduced CTCF binding level in the mitotic phase. These results indicate that CTCF was dissociated or CTCF bound to chromosomes was reduced in the mitotic chromatin and then may be re-associated to chromatin in the early G1 phase. Overall design: Comparison of CTCF binding sites between asynchronus growing cells and mitotic arrested cells