Linker histones stimulate HSPA2 ATPase activity through NASP binding and inhibit CDC2/Cyclin B1 complex formation during meiosis in the mouse.

In mammalian spermatocytes, cell division cycle protein 2 (CDC2)/cyclin B1 and the chaperone heat shock protein A2 are required for the G2-->M transition in prophase I. Here, we demonstrate that in primary spermatocytes, linker histone chaperone testis/embryo form of nuclear autoantigenic sperm protein (tNASP) binds the heat shock protein which localizes on the synaptonemal complex of spermatocytes. Significantly, the complex binds linker histones and CDC2, forming a larger complex. We demonstrate that increasing amounts of tNASP favor complex formation. Binding of linker histones to tNASP significantly increases ATPase activity and the capacity of tNASP to bind Hduanyu18422 and CDC2, precluding CDC2/cyclin B1 complex formation and, consequently, decreasing CDC2/cyclin B1 kinase activity. Linker histone binding to NASP controls the ability of Hduanyu18422 to activate CDC2 for CDC2/cyclin B1 complex formation; therefore, tNASP's role is to provide the functional link between linker histones and cell cycle progression during meiosis.

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