We previously examined the chromatin conformation of the Oct4 gene promoter and its chromatin-remodeling in retinoic acid (RA)-induced differentiation of embryonal carcinoma P19 cells and reported heterochromatinization of the Oct4 gene locus in RA-treated cells, which involved receptor-interacting protein 140 (RIP140) (7). This evidence concerns the gene POU5F1 and embryonal carcinoma.