Identification of telomere-binding proteins by enChIP-MS

We identified the telomere associated molecules by engineered DNA-binding molecule-mediated chromatin immunoprecipitaion (enChIP). Purified proteins were analyzed by GeLC-MS/MS. Tandem mass spectra were extracted by Proteome Discoverer 1.2. Database searchs were submitted to an in-house Mascot server version 2.4.1. Mascot was set up to search the Swissprot database assuming the digestion enzyme as trypsin. Carbamidomethylation of cysteine was set as a fixed modification. Oxidized methionine, acetylation of N terminus and conversion of glutamine to Pyro-Glu at N terminus were set as variable modifications. The precursor mass tolerances were 10 ppm and the tolerance of the MS/MS ions was 0.8 Da. In Scaffold 3.4.5, database search results were grouped according to gel bands.