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Tang Y , Poustovoitov MV , Zhao K , Garfinkel M , Canutescu A , Dunbrack R , D Adams P , Marmorstein R
Structure of a human ASF1a-HIRA complex and insights into specificity of histone chaperone complex assembly
NATURE STRUCTURAL & MOLECULAR BIOLOGY. 2006 Oct;13(10) :921-929
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Abstract
Human HIRA, ASF1a, ASF1b and CAF-1 are evolutionally conserved histone chaperones that form multiple functionally distinct chromatin-assembly complexes, with roles linked to diverse nuclear process, such as DNA replication and formation of heterochromatin in senescent cells. We report the crystal structure of an ASF1a-HIRA heterodimer and a biochemical dissection of ASF1a's mutually exclusive interactions with HIRA and the p60 subunit of CAF-1. The HIRA B domain forms an antiparallel beta-hairpin that binds perpendicular to the strands of the beta-sandwich of ASF1a, via beta-sheet, salt bridge and van der Waals contacts. The N- and C-terminal regions of ASF1a and ASF1b determine the different affinities of these two proteins for HIRA, by contacting regions outside the HIRA B domain. CAF-1 p60 also uses B domain -like motifs for binding to ASF1a, thereby competing with HIRA. Together, these studies begin to define the molecular determinants of assembly of functionally diverse! macromolecular histone chaperone complexes.
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Article 092MZ