1 research outputs found
Altered minorāgroove hydrogen bonds in DNA block transcription elongation by T7 RNA polymerase
DNA transcription depends upon the highly efficient and selective function of RNA polymerases (RNAPs). Modifications in the template DNA can impact the progression of RNA synthesis, and a number of DNA adducts, as well as abasic sites, arrest or stall transcription. Nonetheless, data are needed to understand why certain modifications to the structure of DNA bases stall RNA polymerases while others are efficiently bypassed. In this study, we evaluate the impact that alterations in dNTP/rNTP baseāpair geometry have on transcription. T7 RNA polymerase was used to study transcription over modified purines and pyrimidines with altered Hābonding capacities. The results suggest that introducing wobble baseāpairs into the DNA:RNA heteroduplex interferes with transcriptional elongation and stalls RNA polymerase. However, transcriptional stalling is not observed if mismatched baseāpairs do not Hābond. Together, these studies show that RNAP is able to discriminate mismatches resulting in wobble baseāpairs, and suggest that, in cases of modifications with minor steric impact, DNA:RNA heteroduplex geometry could serve as a controlling factor for initiating transcriptionācoupled DNA repair