 Furthermore, FOXO1-mediated cell cycle arrest is linked with cyclin D1 and cyclin D2 suppression in mammals.It was detected that human FOXO1 is linked with the cyclin D1 promoter using chromatin immunoprecipitation assays (ChIP assays).H215R is a human FOXO1 mutant, which cannot bind to the canonical FRE to induce expression of p27KIP1, repress cyclin D1 and cyclin D2 promoter activity and encourages cell cycle arrest at cyclin G1 (CCNG1).