The DNA Glycosylase Ogg1 is Required for Hypoxia‐induced Activation of VEGF Transcription in Pulmonary Artery Endothelial Cells (PAECs)

Abstract

Hypoxia causes an oxidant stress accompanied by transient oxidative base modifications in hypoxic response elements (HREs) in promoters of inducible nuclear genes. Time‐dependent elimination of the base modifications suggests that they are removed by the base excision pathway of DNA repair (BER), but how DNA repair interacts with transcription is unknown. We tested the idea that suppression of BER by siRNA‐mediated knockdown of the first enzyme in the sequence, Ogg1, altered transcriptional complex formation on the VEGF HRE and attenuated VEGF mRNA expression. Hypoxia increased the number of HRE sequences harboring 8‐oxoG and associating with Hif‐1, as determined by ChIP analysis. While knock‐down of Ogg1 increased the proportion of sequences containing 8‐oxoG, Ogg1 deficiency attenuated Hif‐1 incorporation into the transcriptional complex and reduced VEGF mRNA expression. Knock‐down of Ogg1 expression failed to impact hypoxia‐induced oxidant generation in PAECs nor did it alter the rise in nuclear Hif‐1 or its ability to bind to an oligonucleotide model of the VEGF HRE. These findings indicate that hypoxia causes formation of 8‐oxoG in the VEGF of HRE and suggest that the BER pathway, recruited in response to the hypoxia‐induced oxidative base modifications, may be important for transcriptional activation. Sponsored by NIH.