Acetylation-Mediated Proteasomal Degradation of Core Histones during DNA Repair and Spermatogenesis

Histone acetylation plays critical roles in chromatin remodeling, DNA repair, and epigenetic regulation of gene expression, but the underlying mechanisms are unclear. Proteasomes usually catalyze ATP- and polyubiquitin-dependent proteolysis. Here, we show that the proteasomes containing the activator PA200 catalyze the polyubiquitin-independent degradation of histones. Most proteasomes in mammalian testes (“spermatoproteasomes”) contain a spermatid/sperm-specific α subunit α4 s/PSMA8 and/or the catalytic β subunits of immunoproteasomes in addition to PA200. Deletion of PA200 in mice abolishes acetylation-dependent degradation of somatic core histones during DNA double-strand breaks and delays core histone disappearance in elongated spermatids. Purified PA200 greatly promotes ATP-independent proteasomal degradation of the acetylated core histones, but not polyubiquitinated proteins. Furthermore, acetylation on histones is required for their binding to the bromodomain-like regions in PA200 and its yeast ortholog, Blm10. Thus, PA200/Blm10 specifically targets the core histones for acetylation-mediated degradation by proteasomes, providing mechanisms by which acetylation regulates histone degradation, DNA repair, and spermatogenesis. [Display omitted] •Most proteasomes in mammalian testes are “spermatoproteasomes” that contain PA200•Deletion of PA200 in mice delays core histone disappearance in elongated spermatids•PA200/Blm10 promotes degradation of acetyl-histones during somatic DNA damage•Binding of histones to bromodomain-like regions in PA200/Blm10 depends on acetylation Specialized proteasomes containing the protein PA2000/BLm10 catalyze the degradation of acetylated—rather than ubiquitinated—core histones during spermatogenesis and DNA damage repair.