Histone H2B Ubquitination Regulates Retinoic Acid Signaling through the Cooperation of ASXL1 and BAP1

Abstract

Despite the importance of retinoic acid (RA) signaling and histone monoubiquitination in determining cell fate, the underlying mechanism linking the two processes is poorly explored. We describe that additional sex comb-like 1 (ASXL1) represses RA receptor activity by cooperating with BRCA1-associated protein 1 (BAP1), which contains the ubiquitin C-terminal hydrolase (UCH) domain. Both the UCH- and ASXL1-binding domains of BAP1 were required for cooperation. In contrast to Drosophila BAP1, mammalian BAP1 cleaved ubiquitin from histone H2B. As supported by BAP1 mutants, ASXL1 was critical for BAP1 recruitment to chromatin and its activation therein. ASXL1 requirement was supported using Asxl1 null mice embryonic fibroblasts. Both ASXL1 and BAP1 were downregulated during RA-induced P19 cell differentiation with concomitant increase of ubiquitinated H2B, leading to activation of Hox genes. Our data demonstrate the critical role of ASXL1 cooperation with BAP1 in cell differentiation through the regulation of RA signaling associated with H2B ubiquitination.