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Molecular basis of RanGTP-activated release of Histones H2A-H2B from Importin-9

ABSTRACT: Imp9 is the primary importin for shuttling H2A-H2B from the cytoplasm to the nucleus. It employs an unusual mechanism where the binding of RanGTP is insufficient to release H2A-H2B. The resulting stable RanGTP•Imp9•H2A-H2B complex gains nucleosome assembly activity with H2A-H2B able to be deposited into an assembling nucleosome in vitro. Using hydrogen-deuterium exchange coupled with mass spectrometry (HDX), we show that Imp9 stabilizes H2A-H2B beyond the direct binding site, like other histone chaperones. HDX also shows that binding of RanGTP releases H2A-H2B contacts at Imp9 HEAT repeats 4-5, but not 18-19. DNA- and histone-binding surfaces of H2A-H2B are exposed in the ternary complex, facilitating nucleosome assembly. We also reveal that RanGTP has a weaker affinity for Imp9 when H2A-H2B is bound. Imp9 thus provides a connection between the nuclear import of H2A-H2B and its deposition into chromatin.

INSTRUMENT(S): Synapt MS

ORGANISM(S): Homo Sapiens (human) Xenopus Laevis (african Clawed Frog) Saccharomyces Cerevisiae (baker's Yeast)

DISEASE(S): Malignant Neoplasm Of Ovary,Breast Cancer

SUBMITTER: Sheena D'Arcy

LAB HEAD: Sheena D'Arcy

PROVIDER: PXD037571 | Pride | 2023-06-02

REPOSITORIES: Pride

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	20220609_JS_H2AH2B_100s_1.raw.zip	Raw
	20220609_JS_H2AH2B_100s_2.raw.zip	Raw
	20220609_JS_H2AH2B_100s_3.raw.zip	Raw
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	20220609_JS_H2AH2B_10s_1.raw.zip	Raw

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