Shu complex and RAD52 function in DNA damage recognition and subsequent repair

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PROJECT SUMMARY/ABSTRACT Alkylating agents in our environment from tobacco, pesticides, and produced during drinking water purification cause DNA lesions. These DNA lesions can cause replication fork stalling and lead to DNA double-strand breaks that are canonically repaired by the homologous recombination (HR) pathway. The RAD51 protein plays essential functions in the HR pathway and is regulated by proteins including the Shu complex (SWSAP1- SWS1-PDS5B-SPIDR), BRCA2, RAD52, and CSB. Misregulation of RAD51 regulators leads to genome instability and cancer. Recent studies from our lab and others identified novel additional roles of these proteins in non-canonical repair during DNA lesion recognition, response to replication stress, and transcription coupled repair of replication structures containing R-loops. Mechanistic insight from the yeast Shu complex determined a role during abasic lesion recognition and RAD51-mediated bypass mechanisms during replication. Our work shows that like the yeast Shu complex, the human Shu complex is sensitive to the prototype alkylating agent MMS and depletion of Shu complex components SWSAP1 and SWS1 cause reduced RAD51 foci. Whether the human Shu complex functions by a similar mechanism is unknown. Both RAD52 and Shu components SWSAP1 and SWS1 function during replication restart by an unknown mechanism. RAD52 may use its annealing functions during replication restart and R-loop resolution. The overall goal of this proposed research is to determine how the human Shu complex functions at stalled replication forks to recognize abasic lesions thus enabling either RAD51-dependent strand exchange or RAD52-dependent annealing repair activities. The experiments proposed in this research program will be conducted in two phases. During the mentored K99 phase, I will determine how the Shu complex functions to recognize alkylation-induced lesions like abasic lesions and modulate RAD51-dependent repair using training in cell biology, atomic force microscopy (AFM) and correlative optical tweezers-fluorescence microscopy (CTFM) techniques (Aim 1). During the mentored phase the candidate will take advantage of co-mentoring, resources available at the University of Pittsburgh and the UPMC Hillman Cancer Center for professional development to utilize these skills through research, mentoring, data presentation, and writing opportunities. During the independent R00 phase of the research program, technical skills obtained during the K99 phase will be applied to elucidate the role of Shu complex in RAD52-mediated replication fork restart (Aim 2). Also, during the R00 phase I will extend these approaches into a new area involving resolution of RNA-DNA hybrids by RAD52 protein complexes. These experiments will provide me with the data required for an early independent publication and preliminary data for R-series grants. Importantly, during the R00 phase the candidate will develop independence from their mentor and co-mentors by focusing on the dynamic interplay between the Shu complex and RAD52 in response to replication stress.