Characterization of TCDD-inducible poly-ADP-ribose polymerase (TIPARP/ARTD14) catalytic activity

YesHere, we report the biochemical characterization of the mono-ADP-ribosyltransferase 2,3,7,8-tetrachlorodibenzo-p-dioxin poly-ADP-ribose polymerase (TIPARP/ARTD14/PARP7), which is known to repress aryl hydrocarbon receptor (AHR)-dependent transcription. We found that the nuclear localization of TIPARP was dependent on a short N-terminal sequence and its zinc finger domain. Deletion and in vitro ADP-ribosylation studies identified amino acids 400–657 as the minimum catalytically active region, which retained its ability to mono-ADP-ribosylate AHR. However, the ability of TIPARP to ADP-ribosylate and repress AHR in cells was dependent on both its catalytic activity and zinc finger domain. The catalytic activity of TIPARP was resistant to meta-iodobenzylguanidine but sensitive to iodoacetamide and hydroxylamine, implicating cysteines and acidic side chains as ADP-ribosylated target residues. Mass spectrometry identified multiple ADP-ribosylated peptides in TIPARP and AHR. Electron transfer dissociation analysis of the TIPARP peptide 33ITPLKTCFK41 revealed cysteine 39 as a site for mono-ADP-ribosylation. Mutation of cysteine 39 to alanine resulted in a small, but significant, reduction in TIPARP autoribosylation activity, suggesting that additional amino acid residues are modified, but loss of cysteine 39 did not prevent its ability to repress AHR. Our findings characterize the subcellular localization and mono-ADP-ribosyltransferase activity of TIPARP, identify cysteine as a mono-ADP-ribosylated residue targeted by this enzyme, and confirm the TIPARP-dependent mono-ADP-ribosylation of other protein targets, such as AHR.This work was supported by Canadian Institutes of Health Research (CIHR) operating grants [MOP-494265 and MOP-125919]; CIHR New Investigator Award; an Early Researcher Award from the Ontario Ministry of Innovation [ER10-07-028]; the Johan Throne Holst Foundation; Novo Nordic Foundation; and the Norwegian Cancer Society to J.M. This work was also funded by grants from the Johan Throne Holst Foundation; and the Novo Nordic Foundation to H.I.N

Genome-Wide Profiling of Liver X Receptor, Retinoid X Receptor, and Peroxisome Proliferator-Activated Receptor alpha in Mouse Liver Reveals Extensive Sharing of Binding Sites

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Transcriptional regulation of hepatic lipogenesis

Fatty acid and fat synthesis in liver is a highly regulated metabolic pathway critical for energy distribution. Having common features at their promoter regions, lipogenic genes are coordinately regulated at the transcription level. Transcription factors, such as USF, SREBP-1c, LXR and ChREBP play critical roles in this process. Recently, insights have been gained into how various signaling pathways regulate these transcription factors. After feeding, high blood glucose and insulin induce lipogenic genes through several pathways, including DNA-PK, aPKC and Akt-mTOR. Various transcription factors and coregulators undergo specific modifications, such as phosphorylation, acetylation, or ubiquitination, which affect their function, stability, or localization. Dysregulation of lipogenesis can contribute to hepatosteatosis, which is associated with obesity and insulin resistance