title: A method for genome-wide analysis of DNA helical tension by means of psoralen-DNA photobinding.
abstract: The helical tension of chromosomal DNA is one of the epigenetic landmarks most difficult to examine experimentally. The occurrence of DNA crosslinks mediated by psoralen photobinding (PB) stands as the only suitable probe for assessing this problem. PB is affected by chromatin structure when is done to saturation; but it is mainly determined by DNA helical tension when it is done to very low hit conditions. Hence, we developed a method for genome-wide analysis of DNA helical tension based on PB. We adjusted in vitro PB conditions that discern DNA helical tension and applied them to Saccharomyces cerevisiae cells. We selected the in vivo cross-linked DNA sequences and identified them on DNA arrays. The entire procedure was robust. Comparison of PB obtained in vivo with that obtained in vitro with naked DNA revealed that numerous chromosomal regions had deviated PB values. Similar analyses in yeast topoisomerase mutants uncovered further PB alterations across specific chromosomal domains. These results suggest that distinct chromosome compartments might confine different levels of DNA helical tension in yeast. Genome-wide analysis of psoralen-DNA PB can be, therefore, a useful approach to uncover a trait of the chromosome architecture not amenable to other techniques.
authors.affiliation: Instituto de Biología Molecular de Barcelona-CSIC, Barcelona, Laboratorio de Chips de DNA-SCSIE Universitat de València, Burjassot, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Bermúdez
authors.forename: José
authors.initials: J
authors.lastname: García-Martínez
authors.forename: José E
authors.initials: JE
authors.lastname: Pérez-Ortín
authors.forename: Joaquim
authors.initials: J
authors.lastname: Roca
mesh_terms: D002843:Chromatin / Q000737:chemistry; D015825:Chromosomes, Fungal / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry* / Q000528:radiation effects; D004247:DNA / Q000737:chemistry*; D026942:DNA Topoisomerases / Q000235:genetics; D004271:DNA, Fungal / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000737:chemistry; D023281:Genomics / Q000379:methods; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000737:chemistry; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D011336:Probability; D012441:Saccharomyces cerevisiae / Q000235:genetics; D014158:Transcription, Genetic; D014307:Trioxsalen / Q000737:chemistry* / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D002843:Chromatin; D003432:Cross-Linking Reagents; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D009707:Nucleosomes; D004247:DNA; D026942:DNA Topoisomerases; D014307:Trioxsalen