Regulation of the CRE and GC box activity by 5-formylcytosine, 5-carboxycytosine and 8-oxoguanine
Date issued
Authors
Editors
Journal Title
Journal ISSN
Volume Title
Publisher
License
Abstract
The oxidation-induced DNA modifications 5-formylcytosine (5-fC), 5-carboxycytosine (5-caC) and 8-oxo-7,8-dihydro-2′-deoxyguanine (8-oxoG) were recently implicated in regulating gene expression. However, the specific functions of the three nucleobase modifications at defined loci and the role of Base Excision Repair (BER) in the gene transcription control remain elusive. This investigation aimed to scrutinise the impact of a single 5-fC, 5-caC and 8-oxoG on the activity of cyclic adenosine monophosphate-response element (CRE) and GC box gene regulatory element placed upstream from the RNA polymerase II core promoter.
Quantitative expression analysis in human cells revealed that 5-fC, 5-caC and 8-oxoG caused direct impairment of transcriptional activation. Promoter inhibition by 5-fC and 5-caC differed in the CRE and GC box gene regulatory element, with a particularly strong inhibition by 5-caC in the GC box. Interestingly, GC box inhibition by 8-oxoG was exclusively caused by modified bases in the purine-rich DNA strand. In addition to the negative effects of the primary base modifications on gene expression, BER of 5-fC, 5-caC and 8-oxoG triggered an apurinic-apyrimidinic endonuclease 1-dependent gene silencing mechanism, revealing a notable complexity of transcription regulation by 5-fC, 5-caC and 8-oxoG even in the simplest CRE and GC box promoters.