Ku70 Binding Protein-5 (KUB5), a Novel Factor in Nonhomologous End Joining

Summary

Principal Investigator: David Boothman
Affiliation: University of Texas Southwestern Medical Center
Country: USA
Abstract: DESCRIPTION (provided by applicant): Alterations in DNA repair play major roles in breast cancer resistance to ionizing radiation (IR) and chemotherapies. Factors operating in both DSB repair and RNA transcription, specifically proteins regulating RNA polymerase (Pol) II, have been suggested, but few reported. When RNA Pol II stalls, or when transcription cannot properly terminate, RNA/DNA hybrids (R-loops) have extended half-lives that result in DNA double strand break (DSB) formation and genetic instability. Using yeast two hybrid analyses, we identified Ku70 binding protein #5 [(Kub5)/Hera], a highly conserved human homolog of yeast rtt103 that terminates RNA transcription via its regulation of RNA Pol II. Stable loss of Kub5/Hera expression, either by heterozygote knockout or knockdown by siRNA/shRNA expression, leads to elevated basal DSBs, ATM activation, foci formation and chromatid aberrations that were abrogated by RNase H forced over- expression, suggesting a role for R-loops in genetic instability. Kub5/Hera knockdown cells were hypersensitive to IR, equivalent to Ku70 deficient cells, and failed to repair DSBs that require DNA end-processing. We hypothesize that KUB5/HERA plays dual roles in the cell to: (i) regulate RNA Pol II to terminate RNA transcription via its interaction with the RNA Pol II CTD domain;and (ii) stimulate NHEJ processing of complex DSBs by Ku70 and Artemis interactions. When its expression is depressed (e.g., one-half via haplo-insufficiency) R-loops form and DSBs are created due to deficient RNA transcription termination. DNA damage is simultaneously amplified by the cell's inability to repair DSBs downstream, leading to IR hypersensitivity. Three Specific Aims are proposed: Aim 1: to perform structure/function analyses of Kub5/Hera focusing on two regions, the RPR and coiled-coil domains, to uncouple transcription termination and DSB repair;Aim 2: to define functions of KUB5- Ku70-Artemis complexes in DSB repair;and Aim 3: to define the role(s) of KUB5/HERA in regulating RNA Pol II function, RNA transcription termination, and spontaneous DSB formation and chromatid aberrations. These studies will allow us to explore the role of KUB5/HERA over-expression in human breast cancer radio-resistance. PUBLIC HEALTH RELEVANCE: Human Ku70 binding protein #5, also known as HERA, (KUB5/HERA) is a new factor involved in the repair of DNA ends with complex damage, such as blunt-end breaks. Elevations of KUB5/HERA in breast and ovarian cancers, and our demonstration that KUB5/HERA is extremely important for drug and radiation resistance, suggests that this protein is a valuable target for future therapies and a 'valuable predictor of response'for therapies. Our recent observation that KUB5/HERA is required for RNA termination allows us to also investigate the interface between DNA repair and regulation of RNA Polymerase II and transcription termination.
Funding Period: ----------------2010 - ---------------2015-
more information: NIH RePORT

Top Publications

  1. pmc DNA mismatch repair-dependent activation of c-Abl/p73alpha/GADD45alpha-mediated apoptosis
    Long Shan Li
    Laboratory of Molecular Stress Responses, Department of Oncology, Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
    J Biol Chem 283:21394-403. 2008
  2. pmc Low dose IR-induced IGF-1-sCLU expression: a p53-repressed expression cascade that interferes with TGFβ1 signaling to confer a pro-survival bystander effect
    D Klokov
    Radiological Protection Research and Instrumentation Branch, Chalk River Laboratories, Atomic Energy Canada Limited, Chalk River, ON, USA
    Oncogene 32:479-90. 2013
  3. pmc Cytoplasmic TRADD confers a worse prognosis in glioblastoma
    Sharmistha Chakraborty
    Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX, USA
    Neoplasia 15:888-97. 2013
  4. pmc Opposing effect of EGFRWT on EGFRvIII-mediated NF-κB activation with RIP1 as a cell death switch
    Vineshkumar Thidil Puliyappadamba
    Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
    Cell Rep 4:764-75. 2013
  5. ncbi Review of poly (ADP-ribose) polymerase (PARP) mechanisms of action and rationale for targeting in cancer and other diseases
    Julio Morales
    Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX 75399
    Crit Rev Eukaryot Gene Expr 24:15-28. 2014
  6. pmc Kub5-Hera, the human Rtt103 homolog, plays dual functional roles in transcription termination and DNA repair
    Julio C Morales
    Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX 75390 8807, USA, Department of Biological Sciences, Columbia University, New York, NY 10027, USA, Laboratory of Genetics, Salk Institute of Biological Studies, La Jolla, CA 92037, USA, Department of Radiation Oncology, Case Western Reserve University, Cleveland, OH 44106, USA and Department of Experimental Therapeutics, M D Anderson Cancer Center, Houston, TX 77030, USA
    Nucleic Acids Res 42:4996-5006. 2014

Detail Information

Publications6

  1. pmc DNA mismatch repair-dependent activation of c-Abl/p73alpha/GADD45alpha-mediated apoptosis
    Long Shan Li
    Laboratory of Molecular Stress Responses, Department of Oncology, Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
    J Biol Chem 283:21394-403. 2008
    ..Thus, MMR-dependent intrinsic apoptosis is p53-independent, but stimulated by hMLH1/c-Abl/p73alpha/GADD45alpha retrograde signaling...
  2. pmc Low dose IR-induced IGF-1-sCLU expression: a p53-repressed expression cascade that interferes with TGFβ1 signaling to confer a pro-survival bystander effect
    D Klokov
    Radiological Protection Research and Instrumentation Branch, Chalk River Laboratories, Atomic Energy Canada Limited, Chalk River, ON, USA
    Oncogene 32:479-90. 2013
    ..Thus, sCLU is a pro-survival bystander factor that abrogates TGFβ1 signaling and most likely promotes wound healing...
  3. pmc Cytoplasmic TRADD confers a worse prognosis in glioblastoma
    Sharmistha Chakraborty
    Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX, USA
    Neoplasia 15:888-97. 2013
    ..Thus, our study suggests that increased expression of cytoplasmic TRADD is both an important biomarker and a key driver of NF-κB activation in GBM and supports an oncogenic role for TRADD in GBM...
  4. pmc Opposing effect of EGFRWT on EGFRvIII-mediated NF-κB activation with RIP1 as a cell death switch
    Vineshkumar Thidil Puliyappadamba
    Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
    Cell Rep 4:764-75. 2013
    ..If EGFRWT is overexpressed with EGFRvIII, the addition of EGF leads to a RIP1 kinase-dependent cell death. The EGFRWT-EGFRvIII-RIP1 interplay may regulate oncogenicity and vulnerability to targeted treatment in GBM. ..
  5. ncbi Review of poly (ADP-ribose) polymerase (PARP) mechanisms of action and rationale for targeting in cancer and other diseases
    Julio Morales
    Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX 75399
    Crit Rev Eukaryot Gene Expr 24:15-28. 2014
    ..The PARP pathway and its inhibition thus offers a number of opportunities for therapeutic intervention in both cancer and other disease states. ..
  6. pmc Kub5-Hera, the human Rtt103 homolog, plays dual functional roles in transcription termination and DNA repair
    Julio C Morales
    Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX 75390 8807, USA, Department of Biological Sciences, Columbia University, New York, NY 10027, USA, Laboratory of Genetics, Salk Institute of Biological Studies, La Jolla, CA 92037, USA, Department of Radiation Oncology, Case Western Reserve University, Cleveland, OH 44106, USA and Department of Experimental Therapeutics, M D Anderson Cancer Center, Houston, TX 77030, USA
    Nucleic Acids Res 42:4996-5006. 2014
    ..Artemis re-expression in K-H-deficient cells restored DNA-repair function and resistance to DSB-inducing agents. However, R loops persisted consistent with dual roles of K-H in transcription termination and DSB repair. ..