Summary of requirements for transition from partial to genuine iPSCs. To convert partial iPSCs to genuine iPSCs, at least three major events must occur, that is, repression of genes related to development/differentiation, silencing of retroviral DNAs [32–34], and acquisition of endogenous pluripotency gene expression [6–8]. Our present study indicates that Ccr4-Not complex components and Trim28 at least in part contribute to one of these events, namely repression of developmental genes.