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.

Oxidative DNA Damage and Repair in the Radioresistant Archaeon Thermococcus gammatolerans

“…Cyclonucleosides (in this study, cyclopurines) are classified as complex oxidative DNA lesions presenting, in the same nucleotide, a covalent bond between the C8 of the base and the C5′ of the 2-deoxyribose. In vitro studies show that these bulky lesions are mutagenic and interfere with replication and transcription. − Contrary to small oxidative DNA damage such as oxidized bases, it also appears that cyclopurines are repaired by the nucleotide excision repair system and not by BER enzymes. In parallel to these mechanistic results, measurements of cyclopurine rates in DNA extracted from eukaryotic cultured cells and tissues have been performed by a limited number of research teams.…”

5′,8-Cyclopurine Lesions in DNA Damage: Chemical, Analytical, Biological, and Diagnostic Significance

“…The studies carried out so far suggest three principal directions: (i) If the lesions completely block transcription by RNAPII, multiple genes are inactivated, and consequently, the levels of encoded proteins are reduced, causing neuronal death; (ii) If the lesions partially block transcription by RNAPII, mutant RNA transcripts can be produced, and this can result in mutant proteins that play a role in neuronal death [121]. In addition, the presence of cPu-induced distortion in the DNA structure prevents the binding of transcription factors (TF) [75,122] to DNA, causing reduced or dysregulated gene expression, in turn resulting in neuronal death; (iii) Other possible implications of the presence of cPu lesions in XP have been hypothesized by Arczewska et al [123], who suggest that cPu in XP may impair the ability of BER proteins or other repair proteins to bind to cPu lesions, block transcription, and trigger transcriptomic reprogramming.…”

DNA damage and base excision repair : an important role during zebrafish embryogenesis

“…However, several recent studies suggest that DNA lesions within the cognate sequences of activator protein 1 (AP-1), specificity protein 1 (Sp1) and the nuclear factor kappa-lightchain-enhancer of activated B cells (NF-kB) complex can also alter TF binding (Abraham and Brooks 2011;Ghosh and Mitchell 1999;Ramon et al 1999), indicating that DNA damage within promoter regions may have serious repercussions for cellular physiology. In addition, binding of the p50 subunit to the NF-kB sequence has been shown to shield o G lesions from recognition and repair by OGG1 and Fapy glycosylase (Fpg) suggesting that oxidative DNA damage may be able to persist long enough to affect gene expression (Hailer-Morrison et al 2003).…”