CENP-B creates alternative epigenetic chromatin states permissive for CENP-A or heterochromatin assembly

Abstract

CENP-B binds to CENP-B boxes on centromeric satellite DNAs (alphoid DNA in human). CENP-B maintains kinetochore function through interactions with CENP-A nucleosomes and CENP-C. CENP-B binding to transfected alphoid DNA can induce de novo CENP-A assembly, functional centromere/kinetochore formation and subsequent human artificial chromosome (HAC) formation. On the other hand, CENP-B also facilitates H3K9 tri-methylation on alphoid DNA via Suv39h1 at ectopic alphoid DNA integration sites. Excessive heterochromatin invasion into centromere chromatin suppresses CENP-A assembly. It is unclear how CENP-B controls such different chromatin states. Here, we show that the CENP-B acidic domain recruits histone chaperones and many chromatin modifiers including H3K36 methylase ASH1L, as well as the heterochromatin components, Suv39h1 and HP1s. ASH1L facilitates open chromatin formation competent for CENP-A assembly on alphoid DNA. These results indicate that CENP-B is a nexus for histone modifiers that alternatively promote or suppress CENP-A assembly by mutually exclusive mechanisms. Besides the DNA binding domain, the CENP-B acidic domain also facilitates CENP-A assembly de novo on transfected alphoid DNA. CENP-B therefore balances CENP-A assembly or heterochromatin formation on satellite DNA.