Acts as a transcriptional corepressor in a IRF2-dependent manner; this repression is not mediated by histone deacetylase activities. May act as an E3 ligase towards JDP2, enhancing its polyubiquitination. Represses ATF2-dependent transcriptional activation. . This is the function of Ensembl gene identifier ENSG00000170604 (IRF2BP1, interferon regulatory factor 2 binding protein 1).