Nucleosome Formation Activity of Human Somatic Nuclear Autoantigenic Sperm Protein (sNASP)
Nucleosome Formation Activity of Human Somatic Nuclear Autoantigenic Sperm Protein (sNASP)
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DOI：
10.1074/jbc.m109.083238
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发表时间：
2010-04-16
影响因子：
4.8
通讯作者：
Kurumizaka, Hitoshi
中科院分区：
文献类型：
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作者：
Osakabe, Akihisa;Tachiwana, Hiroaki;Kurumizaka, Hitoshi
核自身抗原精子蛋白（NASP）是N1/N2家族的一员，在真核生物中广泛保守。据报道，人类NASP倾向于与组蛋白H3结合。H4和连接组蛋白H1，与H2A相比。H2B，预计会起到H3的作用。核小体组装的H4伴侣。然而，人类NASP的直接核小体组装活性迄今尚未见报道。在人类中，鉴定出两种剪接异构体，体细胞和睾丸的nasp（分别为sNASP和tNASP）。在本研究中，我们纯化了人类sNASP，发现sNASP有效地促进了含有常规H3.1、H3.2、H3.3或着丝粒特异性CENP-A的核小体的组装。另一方面，sNASP不能有效地促进核小体与H3T（睾丸特异性H3变体）的组装。突变分析表明，H3T的Met-71残基是sNASP形成这种低效率核小体的原因。四体，由H3组成。H4四聚体和没有H2A的DNA。H2B是由snasp介导的核小体组装反应有效形成的。对sNASP的缺失分析表明，sNASP的中心区域26-325个氨基酸残基负责体外核小体组装。这些实验首次证明了人类NASP直接促进核小体组装，并提供了令人信服的证据，证明sNASP是H3.H4的真正的组蛋白伴侣。
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 H3.H4 and the linker histone H1, as compared with H2A.H2B, and is anticipated to function as an H3.H4 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 H3.H4 tetramer and DNA without H2A.H2B, 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 H3.H4.