Pol2-3XHA was immuno-precipitated from HU arrested mrc1 deleted cells.
Extracted molecule
genomic DNA
Extraction protocol
1.5X10^8 cells were disrupted by MULTI-BEADS SHOCKER (MB400U, YASUI KIKAI, Osaka), which was able to keep cells precisely at lower than 6°C during disruption by glass beads. This enabled us to retrieve more than 60% of tagged proteins to soluble fraction routinely. Chromosomal DNA was shared into the average size of 400-600bp by sonication. Anti-HA monoclonal antibody HA.11 (16B12) (CRP Inc., Denver, PA) and anti-FLAG monoclonal antibody M2 (Sigma-Aldrich Co., St Louis, MO) were used for chromatin immuno-precipitation. Immunoprecipitated chromosomal DNA was subsequently purified following the protocol of Young’s lab (Genome wide location analysis web page, MIT). Purified DNA was random primed and amplified by the protocol of Brown’s lab (Stanford). 2ug of amplified DNA was digested with DNaseI to a mean size of 100bp and used for labeling as previously described by Winzeler et al. (Science. 281, 1194-1197, 1998).
Label
biotin-11-ddATP
Label protocol
DNA was end-labelled with Biotin-N6ddATP by Terminal Transferase as previously described by Winzeler et al. (Science. 281, 1194-1197, 1998)
Hybridization protocol
Hybridization, blocking and washing steps were carried out as previously described by Winzeler et al. (Science. 281, 1194-1197, 1998). Each sample was hybridized to the array in 150ul containing 6XSSPE, 0.005% TritonX-100, 15ug fragmented denatured salmon sperm DNA (Gibco-BRL), and 1nmole of a 3’-biotin control oligonucleotide (oligo B2 probes) that hybridized to the border features on the array. Samples were heated to 100°C for 10 min., and then cooled on ice. Samples were hybridized for 16h at 42°C in a hybridization oven (GeneChip hybri oven 320, Affymetrix, CA). Washing and staining protocol (Mini_euk1 ver2) provided by Affymetrix was performed automatically on a fluidics station (GeneChip fluidics station 400, Affymetrix, CA).
Scan protocol
Each array was scanned by HP GeneArray Scanner (Affymetrix, CA) at an emission wavelength of 560nm at 7.5uM resolution. Grids were aligned to the scanned images using the know feature of the array. Primary data analyses were carried out using the Affymetrix Microarray Suite Ver.5.0 software to obtain hybridization intensity, fold change value, change p-value, and detection p-value for each locus.
Description
DNA Pol2 binding profile after 1h in HU. For normalization of this sample WCE (GSM305882) was used.
Data processing
For the discrimination of positive and negative signals for the binding, we compared ChIP fraction with Sup (supernatant) fraction by using three criteria as follows. First, the reliability of strength of signal was judged by detection p-value of each locus (p-value lower than 0.025 was considered as significant). Secondly, reliability of binding ratio was judged by change p-value (p-value lower than 0.025 was considered as significant). Thirdly, clusters consisted of at least three contiguous loci which filled above two criteria were selected as significantly enriched locus, because it is apparent that a single site of protein-DNA interaction will result in immuno-precipitation of DNA fragments that hybridized not only to the locus of the actual binding site but also to its neighbors. This third criterion is very unique, make the data highly reliable and can be only applicable to the chip data obtained by our high-resolution tiling array.
