[3P-1] Poster 3 (3P-01ー3P-47)

[3P-31(WS10-4)] Structural characterization of dynamic changes of histone H3 N-tails through FACT using synergistic structural biology approaches

^○Yasuo Tsunaka¹, Hideaki Ohtomo¹, Kosuke Morikawa², Yoshifumi Nishimura^1,3 (1.Grad. Sch. of Med. Life Sci., Yokohama City Univ., 2.Grad. Sch. of Biostudies, Kyoto Univ., 3.Grad. Sch. of Int. Sci. Life, Hiroshima Univ.)

The FACT complex, comprising SPT16 and SSRP1, conducts nucleosome reorganization. We previously revealed that the phosphorylated acidic intrinsically disordered (pAID) segment of SPT16 within FACT initially binds to the H2B N-tail detached from the nucleosomal DNA by a double strand break [Tsunaka et al., (2016) Genes Dev., 30, 673-686]. In addition, our previous cryo-EM analysis revealed the first intermediate structure of an unwrapped nucleosome with FACT, in which 112-bp DNA and pAID asymmetrically wrapped around the histone core instead of 145-bp DNA [Mayanagi et al., (2019) Sci. Rep., 9, 10183]. Using NMR, here we clarified that the histone H3 N-terminal tails invisible in the cryo-EM structure adopt two different conformations reflecting their asymmetric locations at entry/exit sites: one corresponds to the original nucleosome site buried in two DNA gyres (DNA side), whereas the other, comprising pAID and DNA, is more exposed to the solvent (pAID side) [Tsunaka et al., (2020) iScience 23, 101641]. NMR real-time monitoring showed that H3 acetylation is faster on the pAID side than on the DNA side. NMR spectroscopy and cryo-EM provide a synergistic approach to characterizing dynamic changes of histone H3 N-tails by FACT.