title: Enhanced DNA repair of bleomycin-induced 3'-phosphoglycolate termini at the transcription start sites of actively transcribed genes in human cells.
abstract: The anti-tumour agent, bleomycin, cleaves DNA to give 3'-phosphoglycolate and 5'-phosphate termini. The removal of 3'-phosphoglycolate to give 3'-OH ends is a very important step in the DNA repair of these lesions. In this study, next-generation DNA sequencing was utilised to investigate the repair of these 3'-phosphoglycolate termini at the transcription start sites (TSSs) of genes in HeLa cells. The 143,600 identified human TSSs in HeLa cells comprised 82,596 non-transcribed genes and 61,004 transcribed genes; and the transcribed genes were divided into quintiles of 12,201 genes comprising the top 20%, 20-40%, 40-60%, 60-80%, 80-100% of expressed genes. Repair of bleomycin-induced 3'-phosphoglycolate termini was enhanced at actively transcribed genes. The top 20% and 20-40% quintiles had a very similar level of enhanced repair, the 40-60% quintile was intermediate, while the 60-80% and 80-100% quintiles were close to the low level of enhancement found in non-transcribed genes. There were also interesting differences regarding bleomycin repair on the sense and antisense strands of DNA at TSSs. The sense strand had highly enhanced repair between 0 and 250bp relative to the TSS, while for the antisense strand highly enhanced repair was between 150 and 450bp. Repair of DNA damage is a major mechanism of resistance to anti-tumour drugs and this study provides an insight into this process in human tumour cells.
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia. Electronic address: v.murray@unsw.edu.au.
authors.forename: Vincent
authors.initials: V
authors.lastname: Murray
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Jon K
authors.initials: JK
authors.lastname: Chen
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Galea
mesh_terms: D001761:Bleomycin / Q000494:pharmacology*; D004249:DNA Damage; D004260:DNA Repair; D006016:Glycolates / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D024363:Transcription Initiation Site / Q000187:drug effects*; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D015854:Up-Regulation / Q000235:genetics
chemical_list: D006016:Glycolates; D001761:Bleomycin; C013193:phosphoglycolate
keywords: Anti-tumour agent; Bleomycin; DNA damage; Next-generation sequencing; Phosphoglycolate; Transcription-coupled repair