Journal: Elife / Year: 2017 Title: Cryo-EM structure of the SAGA and NuA4 coactivator subunit Tra1 at 3.7 angstrom resolution. Authors: Luis Miguel Díaz-Santín / Natasha Lukoyanova / Emir Aciyan / Alan Cm Cheung / Abstract: Coactivator complexes SAGA and NuA4 stimulate transcription by post-translationally modifying chromatin. Both complexes contain the Tra1 subunit, a highly conserved 3744-residue protein from the ...Coactivator complexes SAGA and NuA4 stimulate transcription by post-translationally modifying chromatin. Both complexes contain the Tra1 subunit, a highly conserved 3744-residue protein from the Phosphoinositide 3-Kinase-related kinase (PIKK) family and a direct target for multiple sequence-specific activators. We present the Cryo-EM structure of Tra1 to 3.7 Å resolution, revealing an extensive network of alpha-helical solenoids organized into a diamond ring conformation and is strikingly reminiscent of DNA-PKcs, suggesting a direct role for Tra1 in DNA repair. The structure was fitted into an existing SAGA EM reconstruction and reveals limited contact surfaces to Tra1, hence it does not act as a molecular scaffold within SAGA. Mutations that affect activator targeting are distributed across the Tra1 structure, but also cluster within the N-terminal Finger region, indicating the presence of an activator interaction site. The structure of Tra1 is a key milestone in deciphering the mechanism of multiple coactivator complexes.
Conc.: 0.1 mg/ml / Embedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
Specimen support
Grid type: Agar Scientific
Vitrification
Instrument: FEI VITROBOT MARK IV / Cryogen name: ETHANE / Humidity: 94 % / Chamber temperature: 277 K Details: Two subsequent applications of protein were required to achieve the desired particle density on grids. Each application was followed by 20 sec waiting time, with a short 0.5 sec blotting ...Details: Two subsequent applications of protein were required to achieve the desired particle density on grids. Each application was followed by 20 sec waiting time, with a short 0.5 sec blotting after first application and 5 sec blotting after the second.
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Electron microscopy imaging
Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
Microscopy
Model: FEI TITAN KRIOS
Electron gun
Electron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: OTHER
Electron lens
Mode: OTHER / Nominal defocus max: 3500 nm / Nominal defocus min: 1500 nm / Cs: 2.7 mm
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