Fast dividing cells such as cancer cells require high levels of protein synthesis to support cell growth. But when protein synthesis is too high, the proteins cannot be folded accurately resulting in the accumulation of toxic protein aggregates. Hence cells maintain a balance between protein synthesis and protein clearance, to maintain optimum protein levels. Ribosomes are a hub for this regulation: they are the molecular machines that synthesize proteins, and they also recruit a plethora of proteins to assist in protein clearance. Dysregulation of ribosome function is causative for several disorders such as neurodegeneration and cancer. My preliminary data suggests that a cytosolic Poly(ADPribose) Polymerase (PARP) enzyme maintains this protein homeostasis by regulating the function of ribosomes. I have identified proteins in the ribosome complex that could be regulated by this PARP enzyme and this may play a role in maintaining protein homeostasis. In Aim 1, I will characterize how PARP regulates the group of proteins that could play a role in assembling the ribosome to initiate mRNA translation by identifying the complex assembly using mass spectrometric analysis and its effect on translation by targeted purification of polysomal mRNA-sequencing (TRAP-Seq). In Aim 2, I will examine how perturbations to the PARP-regulated ribosome functions will affect protein synthesis and cell growth in vivo. The completion of this application will result in better understanding of the molecular mechanisms and functions of PARP-regulated protein homeostasis, leading to identification of novel therapeutic agents for ovarian cancers.
Dr. Sridevi Challa is a postdoctoral fellow in the laboratory of Dr. W. Lee Kraus lab in the Cecil H. and Ida Green Center for Reproductive Biology Sciences at UT Southwestern Medical Center. She received her Bachelor of Technology degree in Biotechnology from the prestigious Indian Institute of Technology Madras. After working as a Research Associate at the H. Lee Moffitt Cancer Center in Dr. Nupam Mahajan’s lab, she attended the University of South Florida to pursue her doctoral studies in Cancer Biology. During her Ph.D., she studied the mechanisms of activation of IKBKE, a serine/threonine kinase in cancers. Dr. Challa discovered that EGFR with activating mutations phosphorylate and activate IKBKE in non-small cell lung cancers. She has also identified a new potential combinational therapy using IKBKE inhibitors for non-small cell lung cancers and pancreatic cancers. During her graduate studies, she received multiple awards for her submitted abstracts, including Outstanding Poster Awards at the yearly Moffitt Scientific Symposium and Cancer Biology Student Travel Awards from the USF Cancer Biology program. After being awarded a Ph.D. degree in 2017, she joined the Kraus lab to pursue her research interests in the molecular crosstalk between metabolites and signaling pathways in cancer. During her postdoctoral studies, Dr. Challa has collaborated with members of the Kraus lab, and clinical faculty and fellows in the Gynecologic Oncology program in the Department of Obstetrics and Gynecology at UT Southwestern Medical Center. Through these collaborations, she has developed an interest in NAD+
metabolism, rRNA biogenesis and the role of PARP monoenzymes in cancers. She has discovered a new pathway connecting cytoplasmic NAD+
synthesis to the control of mRNA translation and protein homeostasis in ovarian cancers. With the support of funds from Ovarian Cancer Research Alliance, Dr. Challa will elucidate the molecular mechanisms and clinical relevance of this pathway, including therapeutic targeting using novel small molecule inhibitors.