Investigating roles for oxidative guanine damage in transcription regulation

The National Institute of Environmental Health Sciences awarded the Board of Regents of the University of Nebraska $249,000 on September 1, 2026, under the Environmental Health program (CFDA 93.113) to investigate roles for oxidative guanine damage in transcription regulation.

The recipient, operating through its University of Nebraska Medical Center division in Omaha, Nebraska, will conduct research on how 8-oxoguanine (8-oxog) lesions—oxidative DNA damage arising from reactive oxygen species generated by environmental exposures such as air pollution, chemicals, and smoking—affect transcriptional responses in cells. The work focuses on mechanisms by which 8-oxog formation and base-excision-repair processing at guanine-rich genomic regions, particularly at telomeres and gene promoters, regulate gene expression in response to oxidative genotoxic damage. The recipient has developed and will deploy a fluorogen activating peptide (FAP) system that produces singlet oxygen when bound to a photosensitizer dye and excited with far-red light, converting guanine to 8-oxog with high spatial and temporal control. During the R00 (Independent Research) phase of this award, the recipient will test whether 8-oxog processing at promoter sequences and genome-wide modulates transcriptional responses to oxidative stress, building on validation work completed during a prior mentored phase.

The period of performance runs from September 1, 2026, through August 31, 2029. Place of performance is Omaha, Nebraska.

Abstract

(see instructions): excess reactive oxygen species (ROS) arising from endogenous sources and environmental exposures, such as air pollution, chemicals and smoking, cause oxidative stress, a detrimental condition linked to age-related diseases and cancer in humans. Oxidative stress damages all cellular components but is markedly harmful for DNA, where 8 oxoguanine (8-oxog) is among the most prevalent lesions. Cells adopt multiple mechanisms to maintain homeostasis, including mutagenesis prevention and transcriptome reprogramming. Guanine-rich sequences are enriched at telomeres and regulatory regions of the genome and are therefore hot spots for 8-oxog formation. At telomeres, the nucleoprotein caps protecting linear chromosomes, these sequences are transcribed into long non-coding telomere repeat-containing rnas (terra). The formation and base-excision-repair (BER) processing of 8-oxog at g-rich regulatory sequences have been implicated in gene-expression control. However, elucidating the mechanisms of transcriptional modulation by 8-oxog remains challenging, because oxidants used to induce oxidative stress damage multiple cell components and generate diverse DNA adducts. To overcome this, our group validated a fluorogen activating peptide (FAP) system that produces singlet oxygen when bound to a photosensitizer DYE and excited with far-red light, converting guanine into 8-oxog. We report 8-oxog production at telomeres with high spatial and temporal control by fusing the FAP with telomere protein TRF1. For this proposal, FAP has been adapted to target 8-oxog to specific promoter sequences (FAP-DCAS9) or genome-wide (H2B-FAP). The goal of this proposal is to test the hypothesis that the processing of 8-oxog in g-rich genomic regions and promoters regulates transcriptional responses to oxidative genotoxic damage. In the independent R00 phase, the models validated during the K99 phase will be applied, together with technical skills gained from coursework and training with key collaborators, to determine how 8-oxog regulates transcription of specific oxidative-stress-responsive genes at endogenous loci (aim 2, FAP DCAS9). These approaches will be extended genome-wide, using RNA-SEQ, OG-SEQ, drip-SEQ, and chip-SEQ to elucidate the coupling between 8-oxog processing, r-loop formation, and gene expression in response to singlet oxygen produced at chromatin (aim 3, H2B-FAP).