Regulation Of CTCF In Somatic Cell Reprogramming And The Involved Mechanisms

CCCTC binding factor (CTCF) is a highly conserved11zinc finger protein andubiquitously expressed in living organisms. CTCF, the master weaver of the genome,participates in many biological processes, including transcription activation/repression,genome imprinting, chromatin insulation, X chromosome inactivation and high-orderchromatin organization etc.It has been reported that CTCF mediated functionalchromatin interactome in pluripotent cells, however little is known about its roleduring the somatic cell reprogramming process. On the study of the role of CTCFduring such process, we surprisingly found that the expression level of CTCF isrequired for successful reprogramming. In MEF or pre-iPS cells, ectopic expressionof CTCF or knockdown of CTCF through CTCFshRNA or CTCFsiRNA obviouslyinhibited successful colony formation. We also found that neither N terminal nor Cterminal of CTCF has any effect on reprogramming. CTCF could be poly-(ADP-ribosyl)ation modified, by treating with ADP-ribosylation inhibitor3’-ABA,we found that reprogramming was significantly perturbed, even at the late stage3’-ABA treatment could still obviously inhibited the reprogramming process.In orderto further investigate how CTCF influences reprogramming, we performed CTCFChIP-seq in these three cell types. Through bioinformatics analysis, we found thatCTCF binding is highly conserved among the three cell types, meanwhile, CTCFbinding motif is the same among the three cell types, however, the genomicdistribution of CTCF binding sites among the three cell lines is obviously different. Inpre-iPSCs, CTCF co-occupied with RNA polymerase II and plays a role in RNAPolymerase II-dependent transcription. This study will help us to further realize theimportance of CTCF and enrich the functions of CTCF in the mammalian genome.