Project description:Chromatin immunoprecipitation (ChIP) and its derivatives are the main techniques used to determine transcription factor binding sites. However, conventional ChIP with sequencing (ChIP-seq) has problems with poor resolution and newer techniques require significant experimental alterations and complex bioinformatics. Here we build upon our high-resolution crosslinking ChIP-seq (X-ChIP-seq) method and compare it to existing methodologies. By using micrococcal nuclease, which has both endo- and exo-nuclease activity to fragment the chromatin and thereby generate precise protein-DNA footprints, high-resolution X-ChIP-seq achieves single base pair resolution of transcription factor binding. A significant advantage of this protocol is the minimal alteration to the conventional ChIP-seq workflow and simple bioinformatic processing. Using High-resolution X-ChIP-seq we determined the genome-wide binding profile of various DNA binding proteins.
Project description:Kidney cancer accounts for more than 100,000 deaths per year world-wide. More than 80% are clear cell tumors (ccRCCs) and the majority are associated with loss of function of the von Hippel Lindau (pVHL) tumor suppressor resulting in upregulation of HIF-{alpha} subunits, and activation of HIF-dependent transcriptional pathways. Recent GWAS studies have discovered RCC-susceptibility loci both within EPAS1 (HIF-2{alpha}) and in an intergenic region of unknown function on 11q13.3. As part of an ongoing study to define the direct transcriptional targets of HIF-2 in renal cancer, we undertook a genome-wide analysis of HIF-2-binding sites in pVHL-defective 786-O cells (that lack functional HIF-1{alpha} due to a truncated transcript) using chromatin immunoprecipitation with antibodies directed against HIF-2{alpha} and its dimerization partner HIF-1{beta}, coupled to high-throughput sequencing (ChIP-seq). Amongst approximately 600 pangenomic HIF-2{beta} ChIP signals, we observed strong binding (ranked 12th by peak height) almost precisely coinciding with the RCC predisposition SNP rs7105934 on 11q13.3. We report binding of HIF-2{alpha} and HIF-1{beta} in 786-O clear cell renal carcinoma cells. 3 samples examined, HIF-2{alpha}, HIF-1{beta} and pre-immune control ChIP.