Global and phosphoproteomic profiling of the DNA damage response in yeast by SILAC labeling and LC-MS/MS

ABSTRACT: Wild type yeast cells were metabolically labeled in SILAC medium. The heavy (H)-SILAC-labeled cells were then continuously exposed to 0.01% MMS to induce replication stress, and the light (L)-SILAC-labeled cells were mock-exposed. After 3 hours, heavy and light cells were harvested and lysed. To ensure reproducibility, the entire experiment was repeated, and the labels were swapped such that the (L)-SILAC-labeled wild type yeast cells were exposed to 0.01% MMS for 3 hours, and the (H)-SILAC-labeled wild type yeast cells were mock-exposed. Lysates from heavy and light cells were mixed 1:1 by protein mass, reduced and treated with iodoacetamide and then digested with trypsin. 5 mg of each protein lysate was fractionated by high-pH reverse phase (RP) liquid chromatography into 12 samples. For proteome analysis, 2% of each fraction was dried down and re-suspended for LC-MS/MS analysis. The remaining 98% was processed to enrich for phosphopeptides using immobilized metal affinity chromatography (IMAC), dried down, and re-suspended in 0.1% FA, 3% ACN for LC-MS/MS analysis. Global and phosphopeptide-enriched samples were analyzed by LC-MS/MS on a Thermo LTQ-Orbitrap Velos mass spectrometer. Raw MS/MS spectra were searched against version 3.69 of the Yeast International Protein Index (IPI) sequence database using three independent search engines (MaxQuant/Andromeda, Spectrum Mill, and xTandem). All searches were performed with the tryptic enzyme constraint set for up to two missed cleavages, oxidized methionine set as a variable modification, and carbamidomethylated cysteine set as a static modification. For MaxQuant, the peptide MH+ mass tolerances were set at 20 ppm. For X!Tandem, the peptide MH+ mass tolerances were set at ±2.0 Da with post-search filtering of the precursor mass to 50 ppm and the fragment MH+ mass tolerances were set at ±0.5 Da. For Spectrum Mill, peptide MH+ mass tolerances were set at 20 ppm and fragment MH+ mass tolerances were set at ±0.7 Da. The overall FDR was set at ≤3% based on a decoy database search. Phosphosite localization probabilities are reported in the MaxQuant results. Any site with a probability greater than 0.8 was considered to be localized. Quantification of the Heavy:Light ratios was performed using MaxQuant software, with a minimum ratio count of 2 and using unique + razor peptides for quantification.

INSTRUMENT(S): LTQ Orbitrap Velos

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

SUBMITTER: Jacob Kennedy  

LAB HEAD: Amanda G Paulovich

PROVIDER: PXD002344 | Pride | 2016-04-04

REPOSITORIES: Pride