Novel Mechanisms and Regulation of Mammalian Double-Strand Break Repair

Project summary. Cell proliferation under normal and adverse environmental conditions depends on multiple DNA damage response (DDR) pathways. Replicative stress and cellular exposure to genotoxic agents can lead to double- strand breaks (DSBs) which are the most lethal DNA lesions. Major DSB repair (DSBR) pathways include error- prone non-homologous end-joining (NHEJ) and accurate homology-directed repair (HDR) which promotes genome integrity and tumor suppression. Microhomology-mediated end-joining (MMEJ), also referred to as alternative end-joining (alt-EJ) and polymerase theta-mediated end-joining (TMEJ), is the most recently discovered DSBR pathway that contributes to genome instability and cancer cell survival. Over the last 15-20 years, basic research of DSBR has arguably led to some of the most important advances in the history of biomedical science and biotechnology, such as the development of Poly ADP ribose 1 (PARP1) inhibitors as precision medicine for HDR-deficient cancers, and genome engineering involving CRISPR-Cas9 which was the subject of the 2020 Nobel Prize in chemistry. Dr. Pomerantz’s lab has strongly contributed to advancing our knowledge of the molecular mechanisms of MMEJ based DSBR over the past 10 years, and has significantly contributed to advancing our understanding of RNA-templated DSBR (RNA-DNA repair) over the past 5 years. For example, Dr. Pomerantz’s lab recently identified a new MMEJ repair pathway involving Poll, and discovered that human Polq exhibits reverse transcriptase activity and promotes RNA-DNA repair in human cells. To significantly advance our basic knowledge of some of the most intriguing and important areas of DSBR, the Pomerantz lab proposes to continue to address the following three questions: 1. Does RNA directly contribute to DSBR? 2. How are DSBR proteins structurally and chemically regulated? 3. Do undiscovered DSBR pathways exist and contribute to genome instability/integrity?