Such a modification is useful if the protein of interest is directly or closely associated with DNA
Such a modification is useful if the protein of interest is directly or closely associated with DNA. Transfer 45 mL of the tradition to a 250-mL flask and incubate for 5 min at 18 C while shaking (for 5 min at 4 C to collect cells. Remove the supernatant completely by decanting. Wash the cell pellets with 20 mL of cold 1 PBS and centrifuge at 1,000 for 5 min at 4 C. Repeat the wash step (step 5). mM TrisCHCl, pH 7.4. 20 mg/mL proteinase K (dissolved in water and stored at ?20 C). Qiagen QIAquick PCR purification kit, or 10 %10 % Bio-Rad Chelex 100 resin in sterile water. 2.8 Competitive PCR Reaction TaKaRa EXtaq DNA polymerase. 10 EXtaq buffer (TaKaRa). 2.5 mM dNTP mix. 10 M target primer blend ((Fig. 1). In order to facilitate the immunoprecipitation of Rad52, we previously designed cells to express Rad52 fused to 12 tandem copies of the Pk epitope (12Pk) in the C-terminus [28]. The Pk (also called V5) is a short amino acid epitope with the sequence, GKPIPNPLLGLDST, originally found in the paramyxovirus SV5 proteins P and V [29]. The availability of vectors for Pk-epitope tagging in and [28, 30], as well as commercially available anti-Pk antibodies, allow for straightforward and efficient detection and purification of proteins. Additional epitope tags such as 5FLAG, 13Myc, 3HA, GFP, and Faucet can also be used for ChIP, as explained for the 5FLAG tag in our earlier protocol [27]. Representative results of ChIP assays for the Rad52-12Pk protein are demonstrated in Fig. 1. For interpretation of the results, figure legends. Open in a separate windows Fig. 1 TranscriptionCreplication collisions are known to generate genomic instability [41]. ChIP assay of Rad52-12Pk was performed at a control gene-free-region (GFR), and two target sites: and tRNAser-met coding areas. Asynchronous wild-type cells were cultivated at 32 C. ChIP assays were performed using cells cross-linked with formaldehyde and DMA. Rad52-12Pk weakly associated with the GFR region and similar results were acquired at genetic background [31] to reversibly arrest cells in the G2-M boundary at a restrictive heat, 36 C. Then, cells are released into the cell cycle at a permissive heat, 25 C. To monitor cell cycle progression, one can evaluate the septation index by quantifying the appearance of the division IITZ-01 plate (septum) in the cells. In fission candida, septation coincides with S phase (Fig. 2a) and is easily recognized by bright field microscopy. Representative results of septation indices are demonstrated in Fig. 2c. Open in a separate windows Fig. 2 (a) Morphological changes and cell cycle progression of are demonstrated. The cell cycle position can be estimated by analyzing cell length, the number and position of nuclei, and the presence of septum. (b) Morphological changes during septation and a method to count the number of cells are demonstrated. To obtain the septation index, the number of septated cells (mutant cells and grow over night at 25 C. The next day, when OD600 is definitely 0.5, dilute cells into 200 mL YES with a final OD600 of 0.1, incubate at25 C for about 6 h until OD600 reaches 0.2, dilute cells into 600 mL YES, and incubate over night at 25 C (Subheading 3.2). 3.2 Cross-Linking Cells Cross-linking proteins to DNA is a critical step in the ChIP assay. The conditions used in this protocol ensure strong cross-linking. The use of paraformaldehyde IITZ-01 preserves proteinCDNA relationships and CCND2 is suitable for proteins that bind DNA directly. Because many restoration factors are recruited to the DNA indirectly through association with additional DNA-binding proteins, the addition of a proteinCprotein cross-linking agent, such as dimethyl adipimidate (DMA), enables efficient precipitation of more unstable proteinCDNA complexes [32]. Depending on the characteristics of the prospective protein, experts are recommended to optimize the cross-linking conditions. Reducing the percentage of formaldehyde and/or skipping the DMA cross-linking methods should result IITZ-01 in the selective preservation of limited proteinCDNA.