Honors & Awards


  • F99/K00 predoctoral to postdoctoral transition award, National Cancer Institute (National Institutes of Health) (2016-2022)
  • Vanderbilt International Scholar's Program Fellowship, Vanderbilt University (2012-2014)
  • Leon W Cunningham Award for Excellence in Biochemistry, Vanderbilt University (2018)
  • VICC Graduate Student of the year, Vanderbilt Ingram Cancer Center (2017)
  • Chancellor's Gold Medal for Academic Excellence, Anna University, India (2008-2012)

Professional Education


  • Doctor of Philosophy, Vanderbilt University (2018)
  • Bachelor of Technology, Anna University (2012)

Stanford Advisors


All Publications


  • RPA and RAD51: fork reversal, fork protection, and genome stability NATURE STRUCTURAL & MOLECULAR BIOLOGY Bhat, K. P., Cortez, D. 2018; 25 (6): 446–53

    Abstract

    Replication protein A (RPA) and RAD51 are DNA-binding proteins that help maintain genome stability during DNA replication. These proteins regulate nucleases, helicases, DNA translocases, and signaling proteins to control replication, repair, recombination, and the DNA damage response. Their different DNA-binding mechanisms, enzymatic activities, and binding partners provide unique functionalities that cooperate to ensure that the appropriate activities are deployed at the right time to overcome replication challenges. Here we review and discuss the latest discoveries of the mechanisms by which these proteins work to preserve genome stability, with a focus on their actions in fork reversal and fork protection.

    View details for PubMedID 29807999

    View details for PubMedCentralID PMC6006513

  • RADX Modulates RAD51 Activity to Control Replication Fork Protection. Cell reports Bhat, K. P., Krishnamoorthy, A., Dungrawala, H., Garcin, E. B., Modesti, M., Cortez, D. 2018; 24 (3): 538–45

    Abstract

    RAD51 promotes homologous recombination repair (HR) of double-strand breaks and acts during DNA replication to facilitate fork reversal and protect nascent DNA strands from nuclease digestion. Several additional HR proteins regulate fork protection by promoting RAD51 filament formation. Here, we show that RADX modulates stalled fork protection by antagonizing RAD51. Consequently, silencing RADX restores fork protection in cells deficient for BRCA1, BRCA2, FANCA, FANCD2, or BOD1L. Inactivating RADX prevents both MRE11- and DNA2-dependent fork degradation. Furthermore, RADX overexpression causes fork degradation that is dependent on these nucleases and fork reversal. The amount of RAD51 determines the fate of stalled replication forks, with more RAD51 required for fork protection than fork reversal. Finally, we find that RADX effectively competes with RAD51 for binding to single-stranded DNA, supporting a model in which RADX buffers RAD51 to ensure the right amount of reversal and protection to maintain genome stability.

    View details for PubMedID 30021152

  • RADX Promotes Genome Stability and Modulates Chemosensitivity by Regulating RAD51 at Replication Forks MOLECULAR CELL Dungrawala, H., Bhat, K. P., Le Meur, R., Chazin, W. J., Ding, X., Sharan, S. K., Wessel, S. R., Sathe, A. A., Zhao, R., Cortez, D. 2017; 67 (3): 374-+

    Abstract

    RAD51 promotes homology-directed repair (HDR), replication fork reversal, and stalled fork protection. Defects in these functions cause genomic instability and tumorigenesis but also generate hypersensitivity to cancer therapeutics. Here we describe the identification of RADX as an RPA-like, single-strand DNA binding protein. RADX is recruited to replication forks, where it prevents fork collapse by regulating RAD51. When RADX is inactivated, excessive RAD51 activity slows replication elongation and causes double-strand breaks. In cancer cells lacking BRCA2, RADX deletion restores fork protection without restoring HDR. Furthermore, RADX inactivation confers chemotherapy and PARP inhibitor resistance to cancer cells with reduced BRCA2/RAD51 pathway function. By antagonizing RAD51 at forks, RADX allows cells to maintain a high capacity for HDR while ensuring that replication functions of RAD51 are properly regulated. Thus, RADX is essential to achieve the proper balance of RAD51 activity to maintain genome stability.

    View details for PubMedID 28735897

    View details for PubMedCentralID PMC5548441

  • The Replication Checkpoint Prevents Two Types of Fork Collapse without Regulating Replisome Stability MOLECULAR CELL Dungrawala, H., Rose, K. L., Bhat, K. P., Mohni, K. N., Glick, G. G., Couch, F. B., Cortez, D. 2015; 59 (6): 998–1010

    Abstract

    The ATR replication checkpoint ensures that stalled forks remain stable when replisome movement is impeded. Using an improved iPOND protocol combined with SILAC mass spectrometry, we characterized human replisome dynamics in response to fork stalling. Our data provide a quantitative picture of the replisome and replication stress response proteomes in 32 experimental conditions. Importantly, rather than stabilize the replisome, the checkpoint prevents two distinct types of fork collapse. Unsupervised hierarchical clustering of protein abundance on nascent DNA is sufficient to identify protein complexes and place newly identified replisome-associated proteins into functional pathways. As an example, we demonstrate that ZNF644 complexes with the G9a/GLP methyltransferase at replication forks and is needed to prevent replication-associated DNA damage. Our data reveal how the replication checkpoint preserves genome integrity, provide insights into the mechanism of action of ATR inhibitors, and will be a useful resource for replication, DNA repair, and chromatin investigators.

    View details for PubMedID 26365379

    View details for PubMedCentralID PMC4575883

  • High-affinity DNA-binding Domains of Replication Protein A (RPA) Direct SMARCAL1-dependent Replication Fork Remodeling JOURNAL OF BIOLOGICAL CHEMISTRY Bhat, K. P., Betous, R., Cortez, D. 2015; 290 (7): 4110–17

    Abstract

    SMARCAL1 catalyzes replication fork remodeling to maintain genome stability. It is recruited to replication forks via an interaction with replication protein A (RPA), the major ssDNA-binding protein in eukaryotic cells. In addition to directing its localization, RPA also activates SMARCAL1 on some fork substrates but inhibits it on others, thereby conferring substrate specificity to SMARCAL1 fork-remodeling reactions. We investigated the mechanism by which RPA regulates SMARCAL1. Our results indicate that although an interaction between SMARCAL1 and RPA is essential for SMARCAL1 activation, the location of the interacting surface on RPA is not. Counterintuitively, high-affinity DNA binding of RPA DNA-binding domain (DBD) A and DBD-B near the fork junction makes it easier for SMARCAL1 to remodel the fork, which requires removing RPA. We also found that RPA DBD-C and DBD-D are not required for SMARCAL1 regulation. Thus, the orientation of the high-affinity RPA DBDs at forks dictates SMARCAL1 substrate specificity.

    View details for PubMedID 25552480

    View details for PubMedCentralID PMC4326820