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Two small enzyme isoforms mediate mammalian mitochondrial poly(ADP-ribose) glycohydrolase (PARG) activity.

ABSTRACT: Poly(ADP-ribose)glycohydrolase (PARG) is the major enzyme capable of rapidly hydrolyzing poly(ADP-ribose) (PAR) formed by the diverse members of the PARP enzyme family. This study presents an alternative splice mechanism by which two novel PARG protein isoforms of 60 kDa and 55 kDa are expressed from the human PARG gene, termed hPARG60 and hPARG55, respectively. Homologous forms were found in the mouse (mPARG63 and mPARG58) supporting the hypothesis that expression of small PARG isoforms is conserved among mammals. A PARG protein of approximately 60 kDa has been described for decades but with its genetic basis unknown, it was hypothesized to be a product of posttranslational cleavage of larger PARG isoforms. While this is not excluded entirely, isolation and expression of cDNA clones from different sources of RNA indicate that alternative splicing leads to expression of a catalytically active hPARG60 in multiple cell compartments. A second enzyme, hPARG55, that can be expressed through alternative translation initiation from hPARG60 transcripts is strictly targeted to the mitochondria. Functional studies of a mitochondrial targeting signal (MTS) in PARG exon IV suggest that hPARG60 may be capable of shuttling between nucleus and mitochondria, which would be in line with a proposed function of PAR in genotoxic stress-dependent, nuclear-mitochondrial crosstalk.

SUBMITTER: Meyer RG

PROVIDER: S-EPMC2040269 | biostudies-literature | 2007 Aug

REPOSITORIES: biostudies-literature

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Two small enzyme isoforms mediate mammalian mitochondrial poly(ADP-ribose) glycohydrolase (PARG) activity.

Meyer Ralph G RG Meyer-Ficca Mirella L ML Whatcott Clifford J CJ Jacobson Elaine L EL Jacobson Myron K MK

Experimental cell research 20070419 13

Poly(ADP-ribose)glycohydrolase (PARG) is the major enzyme capable of rapidly hydrolyzing poly(ADP-ribose) (PAR) formed by the diverse members of the PARP enzyme family. This study presents an alternative splice mechanism by which two novel PARG protein isoforms of 60 kDa and 55 kDa are expressed from the human PARG gene, termed hPARG60 and hPARG55, respectively. Homologous forms were found in the mouse (mPARG63 and mPARG58) supporting the hypothesis that expression of small PARG isoforms is cons ...[more]

PMID: 17509564

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Project description:Arrival of the novel SARS-CoV-2 has launched a worldwide effort to identify both pre-approved and novel therapeutics targeting the viral proteome, highlighting the urgent need for efficient drug discovery strategies. Even with effective vaccines, infection is possible, and at-risk populations would benefit from effective drug compounds that reduce the lethality and lasting damage of COVID-19 infection. The CoV-2 MacroD-like macrodomain (Mac1) is implicated in viral pathogenicity by disrupting host innate immunity through its mono (ADP-ribosyl) hydrolase activity, making it a prime target for antiviral therapy. We therefore solved the structure of CoV-2 Mac1 from non-structural protein 3 (Nsp3) and applied structural and sequence-based genetic tracing, including newly determined A. pompejana MacroD2 and GDAP2 amino acid sequences, to compare and contrast CoV-2 Mac1 with the functionally related human DNA-damage signaling factor poly (ADP-ribose) glycohydrolase (PARG). Previously, identified targetable features of the PARG active site allowed us to develop a pharmacologically useful PARG inhibitor (PARGi). Here, we developed a focused chemical library and determined 6 novel PARGi X-ray crystal structures for comparative analysis. We applied this knowledge to discovery of CoV-2 Mac1 inhibitors by combining computation and structural analysis to identify PARGi fragments with potential to bind the distal-ribose and adenosyl pockets of the CoV-2 Mac1 active site. Scaffold development of these PARGi fragments has yielded two novel compounds, PARG-345 and PARG-329, that crystallize within the Mac1 active site, providing critical structure-activity data and a pathway for inhibitor optimization. The reported structural findings demonstrate ways to harness our PARGi synthesis and characterization pipeline to develop CoV-2 Mac1 inhibitors targeting the ADP-ribose active site. Together, these structural and computational analyses reveal a path for accelerating development of antiviral therapeutics from pre-existing drug optimization pipelines.

Dataset Information

Two small enzyme isoforms mediate mammalian mitochondrial poly(ADP-ribose) glycohydrolase (PARG) activity.

Publications

Two small enzyme isoforms mediate mammalian mitochondrial poly(ADP-ribose) glycohydrolase (PARG) activity.

Similar Datasets

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