title: The TREX1 C-terminal region controls cellular localization through ubiquitination.
abstract: TREX1 is an autonomous 3'-exonuclease that degrades DNA to prevent inappropriate immune activation. The TREX1 protein is composed of 314 amino acids; the N-terminal 242 amino acids contain the catalytic domain, and the C-terminal region (CTR) localizes TREX1 to the cytosolic compartment. In this study, we show that TREX1 modification by ubiquitination is controlled by a highly conserved sequence in the CTR to affect cellular localization. Transfection of TREX1 deletion constructs into human cells demonstrated that this sequence is required for ubiquitination at multiple lysine residues through a "non-canonical" ubiquitin linkage. A proteomic approach identified ubiquilin 1 as a TREX1 CTR-interacting protein, and this interaction was verified in vitro and in vivo. Cotransfection studies indicated that ubiquilin 1 localizes TREX1 to cytosolic punctate structures dependent upon the TREX1 CTR and lysines within the TREX1 catalytic core. Several TREX1 mutants linked to the autoimmune diseases Aicardi-Goutières syndrome and systemic lupus erythematosus that exhibit full catalytic function were tested for altered ubiquitin modification and cellular localization. Our data show that these catalytically competent disease-causing TREX1 mutants exhibit differential levels of ubiquitination relative to WT TREX1, suggesting a novel mechanism of dysfunction. Furthermore, these differentially ubiquitinated disease-causing mutants also exhibit altered ubiquilin 1 co-localization. Thus, TREX1 post-translational modification indicates an additional mechanism by which mutations disrupt TREX1 biology, leading to human autoimmune disease.
authors: From the Department of Biochemistry, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157.
authors: Clinton D
authors: CD
authors: Orebaugh
authors: Jason M
authors: JM
authors: Fye
authors: Scott
authors: S
authors: Harvey
authors: Thomas
authors: T
authors: Hollis
authors: John C
authors: JC
authors: Wilkinson
authors: Fred W
authors: FW
authors: Perrino
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020274:Autoimmune Diseases of the Nervous System / Q000378:metabolism; D000071183:Autophagy-Related Proteins; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000737:chemistry* / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D050505:Mutant Proteins / Q000378:metabolism; D009421:Nervous System Malformations / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D013329:Structure-Activity Relationship; D054875:Ubiquitination
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000071183:Autophagy-Related Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050505:Mutant Proteins; D010750:Phosphoproteins; C107792:UBQLN1 protein, human; D005090:Exodeoxyribonucleases; C429526:three prime repair exonuclease 1; D008239:Lysine
keywords: Autoimmune Diseases; DNA; DNA Enzymes; Nucleic Acid; Ubiquitination
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