Mechanisms underlying DNA glycosylase dependent regulation of gene expression

Numerous lethal and mutagenic DNA lesions are formed in each cell of our body, every day. DNA base damage is generated upon exposure to damaging agents present in our environment, food, water and inside cells as natural metabolites. The accumulation of DNA base damage is considered to contribute to the onset of neurological disorders, cancer and to promote ageing. Base excision repair (BER) is the major pathway for the removal of damaged DNA bases. The specificity of BER is determined by DNA glycosylases that recognize damaged bases and initiate the pathway. Besides their role in the genome integrity maintenance increasing amount of evidence indicates that DNA glycosylases modulate gene expression. It is currently however unknown how DNA glycosylases regulate the gene expression. With this project we aim to explore the mechanisms underlying DNA glycosylase dependent transcription regulation. During the course of this project we have discovered that DNA glycosylase AAG associates with actively transcribing RNA polymerase II, through direct binding to the Elongator complex. We further showed that this interaction ensures functional AAG-initiated repair, as well as impacts gene expression, in particular of neurodevelopmental genes. The analysis of AAG role in neurodevelopment indicated that altered AAG status impacts gene expression and DNA damage status. In summary, results of this project shed light on the non-canonical role of DNA glycosylases in regulation of transcriptional programs and gene expression.

The results of this work shed light on fundamental cellular processes and uncover role of DNA repair enzymes in regulation of gene expression. The nature of the project allowed to strengthen international collaborations, as well as to productively utilize interdisciplinary skills. Since the enzymes if focus of this project are central to cellular defense against DNA damaging agents, obtained results will enable to better understand how exposure to alkylating agents impacts human health. Further by unrevealing basic cellular mechanisms, this project has potential to provide basis for advancements in diagnostics and treatment of common human diseases.

In this project I aim to challenge current thinking and by using multi-disciplinary approach to explore how DNA glycosylases act beyond classical DNA repair by regulating gene expression. Base excision repair (BER) is the major pathway for the removal of damaged DNA bases. DNA base damage is generated upon exposure to damaging agents present in our environment, food, water and inside cells as natural metabolites. The accumulation of DNA damage is considered to contribute to the onset of neurodevelopmental disorders, cancer and to promote ageing. The specificity of BER is determined by DNA glycosylases that recognize damaged bases and initiate the pathway. The current view is that a major role of DNA glycosylases is to prevent the fixation of mutations and thus protect against degenerative processes and diseases, such as cancer. However, loss of DNA glycosylases does not lead to premature ageing and only in certain instances results in higher cancer incidence. Interestingly, recent work and our unpublished findings show that loss of DNA glycosylases impairs the gene expression. These results suggest that one fundamental function of DNA glycosylases is to regulate transcriptional networks and suggest DNA glycosylases as possibly important modulators of developmental processes. It is currently unknown how DNA glycosylases regulate the gene expression and consequently affect development. The main hypothesis of the project is that DNA glycosylases, by recognizing damaged DNA bases, regulate gene expression. The aim is to determine molecular mechanisms of DNA glycosylases in coordinating the effect of environmental signals on transcription regulation. We expect that the results from this project will delineate the adverse effects of DNA glycosylase loss on development.