Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
90
result(s) for
"Garvin, Alexander"
Sort by:
SUMO, a small, but powerful, regulator of double-strand break repair
The response to a DNA double-stranded break in mammalian cells is a process of sensing and signalling the lesion. It results in halting the cell cycle and local transcription and in the mediation of the DNA repair process itself. The response is launched through a series of post-translational modification signalling events coordinated by phosphorylation and ubiquitination. More recently modifications of proteins by Small Ubiquitin-like MOdifier (SUMO) isoforms have also been found to be key to coordination of the response (Morris et al. 2009 Nature 462, 886–890 (doi:10.1038/nature08593); Galanty et al. 2009 Nature 462, 935–939 (doi:10.1038/nature08657)). However our understanding of the role of SUMOylation is slight compared with our growing knowledge of how ubiquitin drives signal amplification and key chromatin interactions. In this review we consider our current knowledge of how SUMO isoforms, SUMO conjugation machinery, SUMO proteases and SUMO-interacting proteins contribute to directing altered chromatin states and to repair-protein kinetics at a double-stranded DNA lesion in mammalian cells. We also consider the gaps in our understanding.
This article is part of the themed issue ‘Chromatin modifiers and remodellers in DNA repair and signalling’.
Journal Article
The heart of the city : creating vibrant downtowns for a new century
\"In The Heart of the City, distinguished urban planner Alexander Garvin shares lessons on how to plan for a mix of housing, businesses, and attractions; enhance the public realm; improve mobility; and successfully manage downtown services. Garvin opens the book with diagnoses of downtowns across the United States, including the people, businesses, institutions, and public agencies implementing changes. In a review of prescriptions and treatments for any downtown, Garvin shares brief accounts of both successes and failures of what individuals with very different objectives have done to change their downtowns. The final chapters look at what is possible for downtowns in the future, closing with suggested national, state, and local legislation to create standard downtown business improvement districts to better manage downtowns.\"--Publisher description.
Book
SUMO monoclonal antibodies vary in sensitivity, specificity, and ability to detect types of SUMO conjugate
Monoclonal antibodies (MAb) to members of the Small Ubiquitin-like modifier (SUMO) family are essential tools in the study of cellular SUMOylation. However, many anti-SUMO MAbs are poorly validated, and antibody matching to detection format is without an evidence base. Here we test the specificity and sensitivity of twenty-four anti-SUMO MAbs towards monomeric and polymeric SUMO1-4 in dot-blots, immunoblots, immunofluorescence and immunoprecipitation. We find substantial variability between SUMO MAbs for different conjugation states, for detecting increased SUMOylation in response to thirteen different stress agents, and as enrichment reagents for SUMOylated RanGAP1 or KAP1. All four anti-SUMO4 monoclonal antibodies tested cross-reacted wit SUMO2/3, and several SUMO2/3 monoclonal antibodies cross-reacted with SUMO4. These data characterize the specificity of twenty-four anti-SUMO antibodies across commonly used assays, creating an enabling resource for the SUMO research community.
Journal Article
Isomerization of BRCA1–BARD1 promotes replication fork protection
The integrity of genomes is constantly threatened by problems encountered by the replication fork. BRCA1, BRCA2 and a subset of Fanconi anaemia proteins protect stalled replication forks from degradation by nucleases, through pathways that involve RAD51. The contribution and regulation of BRCA1 in replication fork protection, and how this role relates to its role in homologous recombination, is unclear. Here we show that BRCA1 in complex with BARD1, and not the canonical BRCA1–PALB2 interaction, is required for fork protection. BRCA1–BARD1 is regulated by a conformational change mediated by the phosphorylation-directed prolyl isomerase PIN1. PIN1 activity enhances BRCA1–BARD1 interaction with RAD51, thereby increasing the presence of RAD51 at stalled replication structures. We identify genetic variants of BRCA1–BARD1 in patients with cancer that exhibit poor protection of nascent strands but retain homologous recombination proficiency, thus defining domains of BRCA1–BARD1 that are required for fork protection and associated with cancer development. Together, these findings reveal a BRCA1-mediated pathway that governs replication fork protection.
BRCA1–BARD1 has a role in replication fork protection that is mediated by a mechanism of phosphorylation-targeted isomerization of BRCA1 and is independent of the canonical interaction between BRCA1 and PALB2.
Journal Article
Mechanisms of synthetic lethality between BRCA1/2 and 53BP1 deficiencies and DNA polymerase theta targeting
A synthetic lethal relationship exists between disruption of polymerase theta (Polθ), and loss of either 53BP1 or homologous recombination (HR) proteins, including BRCA1; however, the mechanistic basis of these observations are unclear. Here we reveal two distinct mechanisms of Polθ synthetic lethality, identifying dual influences of 1) whether Polθ is lost or inhibited, and 2) the underlying susceptible genotype. Firstly, we find that the sensitivity of BRCA1/2- and 53BP1-deficient cells to Polθ loss, and 53BP1-deficient cells to Polθ inhibition (ART558) requires RAD52, and appropriate reduction of RAD52 can ameliorate these phenotypes. We show that in the absence of Polθ, RAD52 accumulations suppress ssDNA gap-filling in G2/M and encourage MRE11 nuclease accumulation. In contrast, the survival of BRCA1-deficient cells treated with Polθ inhibitor are not restored by RAD52 suppression, and ssDNA gap-filling is prevented by the chemically inhibited polymerase itself. These data define an additional role for Polθ, reveal the mechanism underlying synthetic lethality between 53BP1, BRCA1/2 and Polθ loss, and indicate genotype-dependent Polθ inhibitor mechanisms.
What underlies the synthetic lethality between BRCA1/2 or 53BP1 loss and Polθ loss is unclear. Here, the authors show that RPA-RAD52-MRE11 drive lethality when Polθ is absent in these cells. In BRCA1/2-deficient cells, sensitivity to Polθ inhibition additionally depends on the inhibited protein.
Journal Article
PIN1-SUMO2/3 motif suppresses excessive RNF168 chromatin accumulation and ubiquitin signaling to promote IR resistance
RNF168 is an E3 ubiquitin ligase critical to the mammalian DNA double-strand break repair response. The protein is recruited to and amplifies ubiquitin signals at damaged chromatin and, if not properly regulated, can drive an uncontrolled ubiquitin cascade potentially harmful to repair outcomes. Several indirect mechanisms restrict RNF168 positive feedback, and a longstanding question has been whether these alone suppress excessive RNF168 signaling or whether mechanisms to remove RNF168 from damaged chromatin exist. Here, we reveal a cascade of post-translational modifications which act at three adjacent amino acids, threonine-208, proline-209 and lysine-210, to process RNF168 actively. Phosphorylation at threonine-208 by CDK1/2 induces interaction with the peptidyl-prolyl isomerase PIN1. PIN1 promotes RNF168 SUMOylation at lysine-210, resulting in p97/VCP mediated removal. These actions promote RNF168 clearance and limit RNF168 chromatin build-up. Thus, single amino acid substitutions of the regulatory motif (SUMO-PIN1-assisted Chromatin Regulator, SPaCR) that restrict PIN1 interaction or SUMOylation are sufficient to drive supraphysiological accumulation of RNF168, increased ubiquitin signaling, excessive 53BP1 recruitment and radiosensitivity. Our findings define a mechanism of direct RNF168 regulation that is part of the normal damage response, promoting RNF168 dissociation from chromatin and limiting deleterious ubiquitin signaling.
The ubiquitin ligase, RNF168, promotes DNA break repair but must be regulated to prevent run-away ubiquitin signaling. Here, the authors identify a three-step post-translational cascade regulating RNF168 chromatin removal, acting to suppress excessive signaling and radiosensitivity.
Journal Article
The proteasomal de-ubiquitinating enzyme POH1 promotes the double-strand DNA break response
The regulation of Ubiquitin (Ub) conjugates generated by the complex network of proteins that promote the mammalian DNA double‐strand break (DSB) response is not fully understood. We show here that the Ub protease POH1/rpn11/PSMD14 resident in the 19S proteasome regulatory particle is required for processing poly‐Ub formed in the DSB response. Proteasome activity is required to restrict tudor domain‐dependent 53BP1 accumulation at sites of DNA damage. This occurs both through antagonism of RNF8/RNF168‐mediated lysine 63‐linked poly‐Ub and through the promotion of JMJD2A retention on chromatin. Consistent with this role POH1 acts in opposition to RNF8/RNF168 to modulate end‐joining DNA repair. Additionally, POH1 acts independently of 53BP1 in homologous recombination repair to promote RAD51 loading. Accordingly, POH1‐deficient cells are sensitive to DNA damaging agents. These data demonstrate that proteasomal POH1 is a key de‐ubiquitinating enzyme that regulates ubiquitin conjugates generated in response to damage and that several aspects of the DSB response are regulated by the proteasome.
The POH1/Rpn11 de‐ubiquitinase edits ubiquitin chain signals at DNA damage sites, thereby modulating recruitment of break repair factors such as 53BP1 and RAD51.
Journal Article
USP50 suppresses alternative RecQ helicase use and deleterious DNA2 activity during replication
Mammalian DNA replication relies on various DNA helicase and nuclease activities to ensure accurate genetic duplication, but how different helicase and nuclease activities are properly directed remains unclear. Here, we identify the ubiquitin-specific protease, USP50, as a chromatin-associated protein required to promote ongoing replication, fork restart, telomere maintenance, cellular survival following hydroxyurea or pyridostatin treatment, and suppression of DNA breaks near GC-rich sequences. We find that USP50 supports proper WRN-FEN1 localisation at or near stalled replication forks. Nascent DNA in cells lacking USP50 shows increased association of the DNA2 nuclease and RECQL4 and RECQL5 helicases and replication defects in cells lacking USP50, or FEN1 are driven by these proteins. Consequently, suppression of DNA2 or RECQL4/5 improves USP50-depleted cell resistance to agents inducing replicative stress and restores telomere stability. These data define an unexpected regulatory protein that promotes the balance of helicase and nuclease use at ongoing and stalled replication forks.
Mammalian DNA replication relies on various helicases and nucleases to ensure accurate genetic duplication, but how these enzymes are properly directed is unclear. Here, the authors identify USP50 as a key protein for promoting ongoing replication, restarting stalled forks, maintaining telomeres, and ensuring cell survival.
Journal Article
The deSUMOylase SENP7 promotes chromatin relaxation for homologous recombination DNA repair
SUMO conjugation is known to occur in response to double‐stranded DNA breaks in mammalian cells, but whether SUMO deconjugation has a role remains unclear. Here, we show that the SUMO/Sentrin/Smt3‐specific peptidase, SENP7, interacts with the chromatin repressive KRAB‐associated protein 1 (KAP1) through heterochromatin protein 1 alpha (HP1α). SENP7 promotes the removal of SUMO2/3 from KAP1 and regulates the interaction of the chromatin remodeler CHD3 with chromatin. Consequently, in the presence of CHD3, SENP7 is required for chromatin relaxation in response to DNA damage, for homologous recombination repair and for cellular resistance to DNA‐damaging agents. Thus, deSUMOylation by SENP7 is required to promote a permissive chromatin environment for DNA repair.
This study shows that SENP7 removes SUMO from KAP1, regulating the interaction of CHD3 with chromatin. In the presence of CHD3, SENP7 is required for chromatin relaxation in response to DNA damage, the ensuing repair and resistance to DNA damaging agents.
Journal Article