title: H2A.Bbd: an X-chromosome-encoded histone involved in mammalian spermiogenesis.
abstract: Despite the identification of H2A.Bbd as a new vertebrate-specific replacement histone variant several years ago, and despite the many in vitro structural characterizations using reconstituted chromatin complexes consisting of this variant, the existence of H2A.Bbd in the cell and its location has remained elusive. Here, we report that the native form of this variant is present in highly advanced spermiogenic fractions of mammalian testis at the time when histones are highly acetylated and being replaced by protamines. It is also present in the nucleosomal chromatin fraction of mature human sperm. The ectopically expressed non-tagged version of the protein is associated with micrococcal nuclease-refractory insoluble fractions of chromatin and in mouse (20T1/2) cell line, H2A.Bbd is enriched at the periphery of chromocenters. The exceedingly rapid evolution of this unique X-chromosome-linked histone variant is shared with other reproductive proteins including those associated with chromatin in the mature sperm (protamines) of many vertebrates. This common rate of evolution provides further support for the functional and structural involvement of this protein in male gametogenesis in mammals.
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 3P6, Canada.
authors.forename: Toyotaka
authors.initials: T
authors.lastname: Ishibashi
authors.forename: Andra
authors.initials: A
authors.lastname: Li
authors.forename: José M
authors.initials: JM
authors.lastname: Eirín-López
authors.forename: Ming
authors.initials: M
authors.lastname: Zhao
authors.forename: Kristal
authors.initials: K
authors.lastname: Missiaen
authors.forename: D Wade
authors.initials: DW
authors.lastname: Abbott
authors.forename: Marvin
authors.initials: M
authors.lastname: Meistrich
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hendzel
authors.forename: Juan
authors.initials: J
authors.lastname: Ausió
mesh_terms: D000818:Animals; D002460:Cell Line; D002843:Chromatin / Q000737:chemistry; D050172:Genes, X-Linked; D006367:HeLa Cells; D006657:Histones / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008297:Male; D051379:Mice; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D012641:Selection, Genetic; D013091:Spermatogenesis / Q000235:genetics; D013094:Spermatozoa / Q000378:metabolism; D013737:Testis / Q000378:metabolism
chemical_list: D002843:Chromatin; D006657:Histones; D020033:Protein Isoforms