Journal Article C-terminal acidic domain of histone chaperone human NAP1 is an efficient binding assistant for histone H2A-H2B, but not H3-H4

Ohtomo, Hideaki  ,  Akashi, Satoko  ,  Moriwaki, Yoshihito  ,  Okuwaki, Mitsuru  ,  Osakabe, Akihisa  ,  Nagata, Kyosuke  ,  Kurumizaka, Hitoshi  ,  Nishimura, Yoshifumi

21 ( 3 )  , pp.252 - 263 , 2016-03 , Wiley
Nucleosome assembly protein 1 (NAP1) binds both the (H3-H4)2 tetramer and two H2A-H2B dimers, mediating their sequential deposition on DNA. NAP1 contains a C-terminal acidic domain (CTAD) and a core domain that promotes dimer formation. Here, we have investigated the roles of the core domain and CTAD of human NAP1 in binding to H2A-H2B and H3-H4 by isothermal calorimetry and native mass spectrometry and compared them with the roles of yeast NAP1. We show that the hNAP1 and yNAP1 dimers bind H2A-H2B by two different modes: a strong endothermic interaction and a weak exothermic interaction. A mutant hNAP1, but not yNAP1, dimer lacking CTAD loses the exothermic interaction and shows greatly reduced H2A-H2B binding activity. The isolated CTAD of hNAP1 binds H2A-H2B only exothermically with relatively stronger binding as compared with the exothermic interaction observed for the full-length hNAP1 dimer. Thus, the two CTADs in the hNAP1 dimer seem to provide binding assistance for the strong endothermic interaction of the core domain with H2A-H2B. By contrast, in the relatively weaker binding of hNAP1 to H3-H4 as compared with yNAP1, CTAD of hNAP1 has no significant role. To our knowledge, this is the first distinct role identified for the hNAP1 CTAD.

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