Partial induced pluripotent cells (iPSCs) are cell lines strayed from normal route from somatic cells to iPSCs and are immortalized. Mouse partial iPSCs are able to convert to real iPSCs by the exposure to 2i condition using MAPK and GSK3? inhibitors. However, the molecular mechanisms of this conversion are totally not known. Our piggyback vector mediated genome-wide screen revealed that Cnot2, one of core components of Ccr4-Not complex participates in this conversion. Subsequent analyses revealed other core components, i.e., Cnot1 and Cnot3 and Trim28 which is known to extensively share genomic binding sites with Cnot3 contribute to this conversion as well. Our bioinformatics analyses indicate that the major role of these factors in the conversion is the down-regulation of developmental genes in partial iPSCs.