Expression Analysis Upon PARP-1 or PARG Knockdown in MCF-7 Cells
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE12952 | GEO | 2009/10/23
SECONDARY ACCESSION(S): PRJNA110805
REPOSITORIES: GEO
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Project description:O-GlcNAc glycosylation is a prevalent protein post-translational modification (PTM) that occurs intracellularly. Previous investigations have demonstrated that O-GlcNAcylation crosstalks with phosphorylation and ubiquitination, but it is unclear whether it interplays with other PTMs. Here we studied its relationship with ADP-ribosylation, which involves decorating target proteins with the ADP-ribose moiety. We discovered that one ADP-ribosylation “eraser”- ADP-ribose glycohydrolase (PARG)- is O-GlcNAcylated at Ser26. O-GlcNAcylation of PARG is essential to maintain its nuclear localization and chromatin association. In hepatocellular carcinoma (HCC) cells, PARG O-GlcNAcylation enhances DNA damage-binding protein 1 (DDB1) poly(ADP-ribosyl)ation (PARylation) and attenuates its ubiquitination. DDB1 is thus stabilized and degrades its downstream targets, such as c-Myc. We further utilized mouse xenograft models and demonstrated that PARG-S26A promoted HCC. Our study thus revealed that PARG O-GlcNAcylation inhibits HCC, and we propose that O-GlcNAc glycosylation may crosstalk with many other PTMs.
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Project description:ARH3/ADPRHL2 and PARG are the major enzymes reversing ADP-ribosylation in vertebrates, yet their functions in vivo remain unclear. ARH3 is the only hydrolase able to removes serine-linked mono(ADP-ribose) (MAR), but is much less efficient than PARG against poly(ADP-ribose) (PAR) chains in vitro. Here, by utilizing ARH3-deficient cells, we demonstrate that endogenous MARylation persists on chromatin throughout the cell cycle including mitosis, and is, surprisingly, well tolerated. Conversely, persistent PARylation is highly toxic and has distinct physiological effects, in particular on active transcription histone marks such as H3K9ac and H3K27ac. Furthermore, we reveal a synthetic lethal interaction between ARH3 and PARG, and identify loss of ARH3 as a mechanism of PARP inhibitor resistance, both of which can be exploited in cancer therapy. Finally, we extend our findings to neurodegeneration, suggesting that patients with inherited ARH3 deficiency suffer from stress-induced pathogenic increase in PARylation that can be mitigated by PARP inhibition.
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