The USP1-UAF1 complex interacts with RAD51AP1 to promote homologous recombination repair

<p>USP1 deubiquitinating enzyme and its stoichiometric binding partner UAF1 play an essential role in promoting DNA homologous recombination (HR) repair in response to various types of DNA damaging agents. Deubiquitination of FANCD2 may be attributed to the key role of USP1-UAF1 complex in regulating HR repair, however whether USP1-UAF1 promotes HR repair independently of FANCD2 deubiquitination is not known. Here we show evidence that the USP1-UAF1 complex has a FANCD2-independent function in promoting HR repair. Proteomic search of UAF1-interacting proteins revealed that UAF1 associates with RAD51AP1, a RAD51-interacting protein implicated in HR repair. We show that UAF1 mediates the interaction between USP1 and RAD51AP1, and that depletion of USP1 or UAF1 led to a decreased stability of RAD51AP1. Protein interaction mapping analysis identified some key residues within RAD51AP1 required for interacting with the USP1-UAF1 complex. Cells expressing the UAF1 interaction-deficient mutant of RAD51AP1 show increased chromosomal aberrations in response to Mitomycin C treatment. Moreover, similar to the RAD51AP1 depleted cells, the cells expressing UAF1-interaction deficient RAD51AP1 display persistent RAD51 foci following DNA damage exposure, indicating that these factors regulate a later step during the HR repair. These data altogether suggest that the USP1-UAF1 complex promotes HR repair via multiple mechanisms: through FANCD2 deubiquitination, as well as by interacting with RAD51AP1.</p

PTEN Physically Interacts with and Regulates E2F1-mediated Transcription in Lung Cancer

<p>PTEN phosphorylation at its C-terminal (C-tail) serine/threonine cluster negatively regulates its tumor suppressor function. However, the consequence of such inhibition and its downstream effects in driving lung cancer remain unexplored. Herein, we ascertain the molecular mechanisms by which phosphorylation compromises PTEN function, contributing to lung cancer. Replacement of the serine/threonine residues with alanine generated PTEN-4A, a phosphorylation-deficient PTEN mutant, which suppressed lung cancer cell proliferation and migration. PTEN-4A preferentially localized to the nucleus where it suppressed E2F1-mediated transcription of cell cycle genes. PTEN-4A physically interacted with the transcription factor E2F1 and associated with chromatin at gene promoters with E2F1 DNA-binding sites, a likely mechanism for its transcriptional suppression function. Deletion analysis revealed that the C2 domain of PTEN was indispensable for suppression of E2F1-mediated transcription. Further, we uncovered cancer-associated C2 domain mutant proteins that had lost their ability to suppress E2F1-mediated transcription, supporting the concept that these mutations are oncogenic in patients. Consistent with these findings, we observed increased PTEN phosphorylation and reduced nuclear PTEN levels in lung cancer patient samples establishing phosphorylation as a bona fide inactivation mechanism for PTEN in lung cancer. Thus, use of small molecule inhibitors that hinder PTEN phosphorylation is a plausible approach to activate PTEN function in the treatment of lung cancer.</p> <p>AbbreviationsAKT</p><p>V-Akt Murine Thymoma Viral Oncogene</p>CA<p>Cancer adjacent</p>CDK1<p>Cyclin dependent kinase 1</p>CENPC-C<p>Centromere Protein C</p>ChIP<p>Chromatin Immunoprecipitation</p>co-IP<p>Co-immunoprecipitation</p>COSMIC<p>Catalog of Somatic Mutations In Cancer</p>CREB<p>cAMP Responsive Element Binding Protein</p>C-tail<p>Carboxy terminal tail</p>E2F1<p>E2F Transcription Factor 1</p>ECIS<p>Electric Cell-substrate Impedance Sensing</p>EGFR<p>Epidermal Growth Factor Receptor</p>GSI<p>Gamma Secretase Inhibitor</p>HDAC1<p>Histone Deacetylase 1</p>HP1<p>Heterochromatin protein 1</p>KAP1/TRIM28<p>KRAB-Associated Protein 1/Tripartite Motif Containing 28</p>MAF1<p>Repressor of RNA polymerase III transcription MAF1 homolog</p>MCM2<p>Minichromosome Maintenance Complex Component 2</p>miRNA<p>micro RNA</p>MTF1<p>Metal-Regulatory Transcription Factor 1</p>PARP<p>Poly(ADP-Ribose) Polymerase</p>PD-1<p>Programmed Cell Death 1</p>PD-L1<p>Programmed Cell Death 1 Ligand 1</p>PI3K<p>Phosphatidylinositol-4,5-Bisphosphate 3-Kinase</p>PLK<p>Polo-like Kinase</p>pPTEN<p>Phosphorylated PTEN</p>PTEN<p>Phosphatase and Tensin Homolog deleted on chromosome ten</p>PTM<p>Post Translational Modification</p>Rad51<p>RAD51 Recombinase</p>Rad52<p>RAD52 Recombinase</p>RPA1<p>Replication protein A</p>SILAC<p>Stable Isotope Labeling with Amino Acids in Cell Culture</p>SRF<p>Serum Response Factor</p>TKI<p>Tyrosine Kinase inhbitors</p>TMA<p>Tissue Microarray</p>TOP2A<p>DNA Topoisomerase 2A</p><p></p> <p>V-Akt Murine Thymoma Viral Oncogene</p> <p>Cancer adjacent</p> <p>Cyclin dependent kinase 1</p> <p>Centromere Protein C</p> <p>Chromatin Immunoprecipitation</p> <p>Co-immunoprecipitation</p> <p>Catalog of Somatic Mutations In Cancer</p> <p>cAMP Responsive Element Binding Protein</p> <p>Carboxy terminal tail</p> <p>E2F Transcription Factor 1</p> <p>Electric Cell-substrate Impedance Sensing</p> <p>Epidermal Growth Factor Receptor</p> <p>Gamma Secretase Inhibitor</p> <p>Histone Deacetylase 1</p> <p>Heterochromatin protein 1</p> <p>KRAB-Associated Protein 1/Tripartite Motif Containing 28</p> <p>Repressor of RNA polymerase III transcription MAF1 homolog</p> <p>Minichromosome Maintenance Complex Component 2</p> <p>micro RNA</p> <p>Metal-Regulatory Transcription Factor 1</p> <p>Poly(ADP-Ribose) Polymerase</p> <p>Programmed Cell Death 1</p> <p>Programmed Cell Death 1 Ligand 1</p> <p>Phosphatidylinositol-4,5-Bisphosphate 3-Kinase</p> <p>Polo-like Kinase</p> <p>Phosphorylated PTEN</p> <p>Phosphatase and Tensin Homolog deleted on chromosome ten</p> <p>Post Translational Modification</p> <p>RAD51 Recombinase</p> <p>RAD52 Recombinase</p> <p>Replication protein A</p> <p>Stable Isotope Labeling with Amino Acids in Cell Culture</p> <p>Serum Response Factor</p> <p>Tyrosine Kinase inhbitors</p> <p>Tissue Microarray</p> <p>DNA Topoisomerase 2A</p