For CAR2 complementation, a 3,242 bp fragment amplified by oligos C1500f and Rt080 was 5′-phosphorylated
and inserted to HindIII digested and blunt-ended pDXP795hptR to generate the complementation plasmid (Additional file 5B). Using the same strategy for gene deletion vectors, the deletion region of STE20 and URA3 were amplified using oligos STE20Lf/STE20Rr (2,196 bp) and Rt33/Rt34 (2,784 bp), cloned into pEX2 and digested using BspHI/NcoI and StuI/MfeI (blunt-ended) to create Selleckchem SAR245409 pKOSTE20 and pKOURA3, respectively. Transformation and identification of transformants ATMT and fungal colony PCR were both performed as described previously . For further identification of gene deletion mutants, multiplex PCR  using genomic DNA as the template was performed to
prevent false negative results. Two sets of primer pairs, one specific to the deletion target (Rg70f3/Rg70r2 and Rt096/Rt097 for KU70 and CAR2 gene, respectively) and the other to the reference gene GPD1 (Rt006 and Rt007) were added to the reactions. Isolation of genomic DNA, RNA and Southern blot analysis Cell cultures at exponential stage were collected and genomic DNA was extracted using MasterPure™ Yeast DNA purification kit (Epicentre, Madison, WI, USA), while RNA was extracted as described previously . The concentrations of extracted DNA or RNA samples were determined with NanoDrop® ND-1000 Spectrophotometer (Thermo Scientific, Wilmington, DE, USA) and this website their integrity were checked by agarose gel electrophoresis. For Southern blot analysis, 10 μg of genomic DNA was digested with PvuI at 37°C for about 24 hrs and resolved Oxalosuccinic acid by electrophoresis in a 0.8% agarose gel. Southern
hybridization and detection procedures were performed using DIG (digoxigenin)-High Prime DNA Labeling and Detection kit in accordance with the manufacturer’s instructions (DIG Application Manual for Filter Hybridization, Roche Diagnostics, Indiana, IA, USA). The probes were amplified by PCR labeling using DIG DNA labeling mix, with primers Rt100 and Rt101 used to amplify a fragment targeting the 5′ flanking sequence of KU70, and Rt083 and Rt084 specific to the 5′ flanking sequence of CAR2. Sensitivity to DNA-damaging agents MMS and UV radiation were the DNA-damaging agents used to analyze strain sensitivity monitored by spot plate assay. Cell cultures in YPD broth were adjusted to one OD600 unit and 10-fold serial diluted, from which the diluted samples were spotted on YPD agar plates supplemented with MMS (Sigma, MO, USA) ranging from 0.001-0.1%. Exposure to UV radiation was done by placing the plates in a UV Crosslinker (Spectrolinker™ XL-1000, Spectronics Corporation, NY, USA) at a dose ranging from 100 to 600 J/m2 after the samples were spotted. Photomicroscopy Freshly cultured cells were analyzed using a Nikon Eclipse 80i microscope equipped with CFI Plan Apochromat objectives (Nikon, Melville, NY, USA).