National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R35GM141461
United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R01GM069909
United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
T32GM008203
United States
Welch Foundation
I-1532
United States
Cancer Prevention and Research Institute of Texas (CPRIT)
RP220582
United States
Citation
Journal: J Cell Biol / Year: 2025 Title: Nap1 and Kap114 co-chaperone H2A-H2B and facilitate targeted histone release in the nucleus. Authors: Ho Yee Joyce Fung / Jenny Jiou / Ashley B Niesman / Natalia E Bernardes / Yuh Min Chook / Abstract: Core histones, synthesized and processed in the cytoplasm, must be chaperoned as they are transported into the nucleus for nucleosome assembly. The importin Kap114 transports H2A-H2B into the yeast ...Core histones, synthesized and processed in the cytoplasm, must be chaperoned as they are transported into the nucleus for nucleosome assembly. The importin Kap114 transports H2A-H2B into the yeast nucleus, where RanGTP facilitates histone release. Kap114 and H2A-H2B also bind the histone chaperone Nap1, but how Nap1 and Kap114 cooperate in transport and nucleosome assembly remains unclear. Here, biochemical and structural analyses show that Kap114, H2A-H2B, and a Nap1 dimer (Nap12) associate in the absence and presence of RanGTP to form equimolar complexes. A previous study had shown that RanGTP reduces Kap114's ability to chaperone H2A-H2B, but a new cryo-EM structure of the Nap12•H2A-H2B•Kap114•RanGTP complex explains how both Kap114 and Nap12 interact with H2A-H2B, restoring its chaperoning within the assembly while effectively depositing it into nucleosomes. Together, our results suggest that Kap114 and Nap12 provide a sheltered path that facilitates the transfer of H2A-H2B from Kap114 to Nap12, ultimately directing its specific deposition into nucleosomes.
Entire : Complex of Kap114 bound to Ran GTPase Gsp1, H2A-H2B and Nap1
Entire
Name: Complex of Kap114 bound to Ran GTPase Gsp1, H2A-H2B and Nap1
Components
Complex: Complex of Kap114 bound to Ran GTPase Gsp1, H2A-H2B and Nap1
-
Supramolecule #1: Complex of Kap114 bound to Ran GTPase Gsp1, H2A-H2B and Nap1
Supramolecule
Name: Complex of Kap114 bound to Ran GTPase Gsp1, H2A-H2B and Nap1 type: complex / ID: 1 / Parent: 0 / Macromolecule list: #1-#6 Details: Complex was formed and dialyzed overnight, then mildly crosslinked and separated by size-exclusion chromatography.
Model: Quantifoil R2/1 / Material: COPPER / Mesh: 300 / Support film - Material: CARBON / Support film - topology: HOLEY / Pretreatment - Type: GLOW DISCHARGE / Pretreatment - Time: 80 sec.
Vitrification
Cryogen name: ETHANE / Chamber humidity: 95 % / Chamber temperature: 280 K / Instrument: FEI VITROBOT MARK IV
Details
Crosslinked sample.
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Electron microscopy
Microscope
FEI TITAN KRIOS
Specialist optics
Energy filter - Slit width: 20 eV
Image recording
Film or detector model: FEI FALCON IV (4k x 4k) / Number grids imaged: 1 / Number real images: 9331 / Average exposure time: 3.6 sec. / Average electron dose: 50.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Number selected: 1381753 / Details: Blob picker then followed by Topaz picking.
Startup model
Type of model: NONE / Details: Ab-initio reconstruction.
Final reconstruction
Resolution.type: BY AUTHOR / Resolution: 3.97 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: cryoSPARC Details: Particle subtraction was performed with a mask covering RanGTP and Kap114, and local refinement was performed for Nap1 and H2A-H2B bound region. Number images used: 133516
Initial angle assignment
Type: MAXIMUM LIKELIHOOD / Software - Name: cryoSPARC
Final angle assignment
Type: MAXIMUM LIKELIHOOD / Software - Name: cryoSPARC
Final 3D classification
Software - Name: cryoSPARC
FSC plot (resolution estimation)
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