title: Divergent effects of oxidatively induced modification to the C8 of 2'-deoxyadenosine on transcription factor binding: 8,5'(S)-cyclo-2'-deoxyadenosine inhibits the binding of multiple sequence specific transcription factors, while 8-oxo-2'-deoxyadenosine increases binding of CREB and NF-kappa B to DNA.
abstract: DNA is exposed to endogenous and environmental factors that can form stable lesions. If not repaired, these lesions can lead to transcription/replication blocking or mutagenic bypass. Our previous work has focused on 8,5'-cyclopurine 2'-deoxyribonucleosides, a unique class of oxidatively induced DNA lesions that are specifically repaired by the NER pathway (see Brooks PJ [2008]: DNA Repair 7:1168-1179). Here we used EMSA to monitor the ability of sequence-specific transcription factors, HSF1, CREB, and NF-kappaB and "architectural" transcription factor, HMGA, to bind to their target sequences when 8, 5'(S)-cyclo-2'-deoxyadenosine (cyclo-dAdo) is present within their recognition sequences. For comparison, we also tested the effect of 8-oxo-7,8-dihydro-2'-deoxyadenosine (8-oxo-dAdo) in the same recognition sequences. The presence of a cyclo-dAdo lesion in the target sequence essentially eliminated the binding activity of HSF1, CREB, and NF-kappa B whereas HMGA retained some of its binding activity. In contrast, 8-oxo-dAdo had no obvious effect on the binding activity of HSF1 and HMGA in comparison to lesion-free DNA. Notably, though, CREB and NFκB binding increased when an 8-oxo-dAdo lesion was present in their target sequence. Competition EMSA showed about 2-3-fold increased affinity of both proteins for the 8-oxo-dAdo containing target sequence compared to lesion-free DNA. Molecular modeling of the lesions in the NF-kappaB sequence indicated that 8-oxo-dAdo may form an additional hydrogen bond with the protein, thereby strengthening the binding of NF-kappa B to its DNA target. The cyclo-dAdo lesion, in contrast, distorted the DNA structure, providing an explanation for the inhibition of NF-kappaB binding.
authors.affiliation: Section on Molecular Neurobiology, Laboratory of Neurogenetics, National Institute on Alcohol Abuse and Alcoholism, Rockville, Maryland 20852, USA.
authors.forename: Jessy
authors.initials: J
authors.lastname: Abraham
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Brooks
mesh_terms: D000818:Animals; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry; D003839:Deoxyadenosines / Q000737:chemistry*; D024003:HMGA Proteins / Q000737:chemistry; D000076249:Heat Shock Transcription Factors; D006801:Humans; D051379:Mice; D016328:NF-kappa B / Q000737:chemistry*; D018384:Oxidative Stress; D011485:Protein Binding; D014157:Transcription Factors / Q000737:chemistry
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D003839:Deoxyadenosines; D024003:HMGA Proteins; D000076249:Heat Shock Transcription Factors; C490017:Hsf1 protein, mouse; D016328:NF-kappa B; D014157:Transcription Factors; C056752:8,5'-cyclo-2'-deoxyadenosine; C078251:2'-deoxy-7,8-dihydro-8-oxoadenosine; D004247:DNA; C058118:2'-deoxyadenosine