Nucleosome Formation Activity of Human Somatic Nuclear Autoantigenic Sperm Protein (sNASP)

Abstract

NASP (nuclear autoantigenic sperm protein) is a member of the N1/N2 family, which is widely conserved among eukaryotes. Human NASP reportedly prefers to bind to histones H3⅐H4 and the linker histone H1, as compared with H2A⅐H2B, and is anticipated to function as an H3⅐H4 chaperone for nucleosome assembly. However, the direct nucleosome assembly activity of human NASP has not been reported so far. In humans, two spliced isoforms, somatic and testicular NASPs (sNASP and tNASP, respectively) were identified. In the present study we purified human sNASP and found that sNASP efficiently promoted the assembly of nucleosomes containing the conventional H3.1, H3.2, H3.3, or centromere-specific CENP-A. On the other hand, sNASP inefficiently promoted nucleosome assembly with H3T, a testis-specific H3 variant. Mutational analyses revealed that the Met-71 residue of H3T is responsible for this inefficient nucleosome formation by sNASP. Tetrasomes, composed of the H3⅐H4 tetramer and DNA without H2A⅐H2B, were efficiently formed by the sNASP-mediated nucleosome-assembly reaction. A deletion analysis of sNASP revealed that the central region, amino acid residues 26 -325, of sNASP is responsible for nucleosome assembly in vitro. These experiments are the first demonstration that human NASP directly promotes nucleosome assembly and provide compelling evidence that sNASP is a bona fide histone chaperone for H3⅐H4.

Epigenetic Regulation of the Blimp-1 Gene (Prdm1) in B Cells Involves Bach2 and Histone Deacetylase 3

“…Therefore, Rif1 may recruit additional histone-modifying enzymes such as those to the Prdm1 locus. Another interesting category of molecules includes Arid1a (BAF250) and Smarcd2 (BAF60B), which are the components of SWI/SNF chromatin remodelers (43), and Nasp, a histone chaperone (44). The presence of these molecules in the Bach2 complex suggests that chromatin remodeling may also be involved in the repression of Prdm1 and other target genes in B cells.…”

Vertebrate Spt2 is a novel nucleolar histone chaperone that assists in ribosomal DNA transcription

“…SUPT16H and SSRP1 form the FACT complex, which functions as a histone chaperone during transcription, replication and repair (Winkler and Luger, 2011). SUPT6H and NASP are also known as histone chaperones that directly bind to core histones (Bortvin and Winston, 1996;Wang et al, 2008;Osakabe et al, 2010). Thus, our pull-down experiments with the H3/H4 beads were proved to be useful to identify histone-binding proteins in HeLa cell extracts.…”

“…In both the cytoplasmic and chromatin fractions of the cell extracts, we detected several known histone-binding proteins, including MCM2, MCM4, MCM6, MCM7 (Ishimi et al, 1996), SUPT16H (Spt16; FACT140) (Orphanides et al, 1998), SSRP1 (FACT80) (Orphanides et al, 1998), SUPT6H (Spt6) (Bortvin and Winston, 1996), and NASP (Wang et al, 2008;Osakabe et al, 2010). MCM2-4-6-7 is a subcomplex of the MCM2-7 hexamer, which functions as a helicase in replication initiation (Bochman and Schwacha, 2009).…”

Targeting of Arabidopsis KNL2 to Centromeres Depends on the Conserved CENPC-k Motif in Its C Terminus

“…Two cenH3 chaperones have been identified: the Holliday Junction Recognition Protein (HJURP) and the Nuclear Autoantigenic Sperm Protein (Osakabe et al, 2010) in human and their respective homologs Scm3 and Sim3 in yeast (Pidoux et al, 2009). The Mis18 complex mediates the recruitment of HJURP to endogenous centromeres (Foltz et al, 2009;Barnhart et al, 2011).…”