Person: Harper, Jeffrey
Loading...
Email Address
AA Acceptance Date
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
Harper
First Name
Jeffrey
Name
Harper, Jeffrey
5 results
Search Results
Now showing 1 - 5 of 5
Publication Endosomal Rab cycles regulate Parkin-mediated mitophagy(eLife Sciences Publications, Ltd, 2018) Yamano, Koji; Wang, Chunxin; Sarraf, Shireen A; Münch, Christian; Kikuchi, Reika; Noda, Nobuo N; Hizukuri, Yohei; Kanemaki, Masato T; Harper, Jeffrey; Tanaka, Keiji; Matsuda, Noriyuki; Youle, Richard JDamaged mitochondria are selectively eliminated by mitophagy. Parkin and PINK1, gene products mutated in familial Parkinson’s disease, play essential roles in mitophagy through ubiquitination of mitochondria. Cargo ubiquitination by E3 ubiquitin ligase Parkin is important to trigger selective autophagy. Although autophagy receptors recruit LC3-labeled autophagic membranes onto damaged mitochondria, how other essential autophagy units such as ATG9A-integrated vesicles are recruited remains unclear. Here, using mammalian cultured cells, we demonstrate that RABGEF1, the upstream factor of the endosomal Rab GTPase cascade, is recruited to damaged mitochondria via ubiquitin binding downstream of Parkin. RABGEF1 directs the downstream Rab proteins, RAB5 and RAB7A, to damaged mitochondria, whose associations are further regulated by mitochondrial Rab-GAPs. Furthermore, depletion of RAB7A inhibited ATG9A vesicle assembly and subsequent encapsulation of the mitochondria by autophagic membranes. These results strongly suggest that endosomal Rab cycles on damaged mitochondria are a crucial regulator of mitophagy through assembling ATG9A vesicles.Publication A Genetic Screen Identifies FAN1, a Fanconi Anemia-Associated Nuclease Necessary for DNA Interstrand Crosslink Repair(Elsevier BV, 2010) Smogorzewska, Agata; Desetty, Rohini; Saito, Takamune; Schlabach, Michael; Lach, Francis P.; Sowa, Mathew E.; Clark, Alan B.; Kunkel, Thomas A.; Harper, Jeffrey; Colaiacovo, Monica; Elledge, StephenThe Fanconi anemia (FA) pathway is responsible for interstrand crosslink repair. At the heart of this pathway is the FANCI-FAND2 (ID) complex, which, upon ubiquitination by the FA core complex, travels to sites of damage to coordinate repair that includes nucleolytic modification of the DNA urrounding the lesion and translesion synthesis. How the ID complex regulates these events is unknown. Here we describe a shRNA screen that led to the identification of two nucleases necessary for crosslink repair, FAN1 (KIAA1018) and EXDL2. FAN1 colocalizes at sites of DNA damage with the ID complex in a manner dependent on FAN1’s ubiquitin-binding domain (UBZ), the ID complex, and monoubiquitination of FANCD2. FAN1 possesses intrinsic 50 -30 exonuclease activity and endonuclease activity that cleaves nicked and branched structures. We propose that FAN1 is a repair nuclease that is recruited to sites of crosslink damage in part through binding the ubiquitinated ID complex through its UBZ domain.Publication SLX-1 Is Required for Maintaining Genomic Integrity and Promoting Meiotic Noncrossovers in the Caenorhabditis elegans Germline(Public Library of Science, 2012) Saito, Takamune; Mohideen, Firaz; Meyer, Katherine; Harper, Jeffrey; Colaiácovo, Monica P.Although the SLX4 complex, which includes structure-specific nucleases such as XPF, MUS81, and SLX1, plays important roles in the repair of several kinds of DNA damage, the function of SLX1 in the germline remains unknown. Here we characterized the endonuclease activities of the Caenorhabditis elegans SLX-1-HIM-18/SLX-4 complex co-purified from human 293T cells and determined SLX-1 germline function via analysis of slx-1(tm2644) mutants. SLX-1 shows a HIM-18/SLX-4–dependent endonuclease activity toward replication forks, 5′-flaps, and Holliday junctions. slx-1 mutants exhibit hypersensitivity to UV, nitrogen mustard, and camptothecin, but not gamma irradiation. Consistent with a role in DNA repair, recombination intermediates accumulate in both mitotic and meiotic germ cells in slx-1 mutants. Importantly, meiotic crossover distribution, but not crossover frequency, is altered on chromosomes in slx-1 mutants compared to wild type. This alteration is not due to changes in either the levels or distribution of double-strand breaks (DSBs) along chromosomes. We propose that SLX-1 is required for repair at stalled or collapsed replication forks, interstrand crosslink repair, and nucleotide excision repair during mitosis. Moreover, we hypothesize that SLX-1 regulates the crossover landscape during meiosis by acting as a noncrossover-promoting factor in a subset of DSBs.Publication An OBSL1-Cul7\(^{\text{Fbxw8}}\) Ubiquitin Ligase Signaling Mechanism Regulates Golgi Morphology and Dendrite Patterning(Public Library of Science, 2011) Litterman, Nadia Kathryn; Ikeuchi, Yoshiho; Gallardo, Gilbert; O'Connell, Brenda C.; Sowa, Mathew E.; Gygi, Steven; Harper, Jeffrey; Bonni, AzadThe elaboration of dendrites in neurons requires secretory trafficking through the Golgi apparatus, but the mechanisms that govern Golgi function in neuronal morphogenesis in the brain have remained largely unexplored. Here, we report that the E3 ubiquitin ligase Cul7\(^{\text{Fbxw8}}\) localizes to the Golgi complex in mammalian brain neurons. Inhibition of Cul7\(^{\text{Fbxw8}}\) by independent approaches including Fbxw8 knockdown reveals that Cul7\(^{\text{Fbxw8}}\) is selectively required for the growth and elaboration of dendrites but not axons in primary neurons and in the developing rat cerebellum in vivo. Inhibition of Cul7\(^{\text{Fbxw8}}\) also dramatically impairs the morphology of the Golgi complex, leading to deficient secretory trafficking in neurons. Using an immunoprecipitation/mass spectrometry screening approach, we also uncover the cytoskeletal adaptor protein OBSL1 as a critical regulator of Cul7\(^{\text{Fbxw8}}\) in Golgi morphogenesis and dendrite elaboration. OBSL1 forms a physical complex with the scaffold protein Cul7 and thereby localizes Cul7 at the Golgi apparatus. Accordingly, OBSL1 is required for the morphogenesis of the Golgi apparatus and the elaboration of dendrites. Finally, we identify the Golgi protein Grasp65 as a novel and physiologically relevant substrate of Cul7\(^{\text{Fbxw8}}\) in the control of Golgi and dendrite morphogenesis in neurons. Collectively, these findings define a novel OBSL1-regulated Cul7\(^{\text{Fbxw8}}\) ubiquitin signaling mechanism that orchestrates the morphogenesis of the Golgi apparatus and patterning of dendrites, with fundamental implications for our understanding of brain development.Publication A Systematic Analysis of Factors Localized to Damaged Chromatin Reveals PARP-Dependent Recruitment of Transcription Factors(Elsevier BV, 2015-06) Izhar, Lior; Adamson, Britt; Ciccia, Alberto; Lewis, Jedd; Pontano-Vaites, Laura; Leng, Yumei; Westbrook, Thomas F.; Elledge, Stephen; Liang, Anthony; Harper, JeffreyLocalization to sites of DNA damage is a hallmark of DNA damage response (DDR) proteins. To identify DDR factors, we screened epitope-tagged proteins for localization to sites of chromatin damaged by UV laser microirradiation and found >120 proteins that localize to damaged chromatin. These include the BAF tumor suppressor complex and the amyotrophic lateral sclerosis (ALS) candidate protein TAF15. TAF15 contains multiple domains that bind damaged chromatin in a poly-(ADP-ribose) polymerase (PARP)-dependent manner, suggesting a possible role as glue that tethers multiple PAR chains together. Many positives were transcription factors; > 70% of randomly tested transcription factors localized to sites of DNA damage, and of these, similar to 90% were PARP dependent for localization. Mutational analyses showed that localization to damaged chromatin is DNA-binding-domain dependent. By examining Hoechst staining patterns at damage sites, we see evidence of chromatin decompaction that is PARP dependent. We propose that PARP-regulated chromatin remodeling at sites of damage allows transient accessibility of DNA-binding proteins.