A novel E3 ubiquitin ligase TRAC-1 positively regulates T cell activation.
TRAC-1 (T cell RING (really interesting new gene) protein identified in activation screen) is a novel E3 ubiquitin ligase identified from a retroviral vector-based T cell surface activation marker screen. The C-terminal truncated TRAC-1 specifically inhibited anti-TCR-mediated CD69 up-regulation in Jurkat cells, a human T leukemic cell line. In this study, we show that TRAC-1 is a RING finger ubiquitin E3 ligase with highest expression in lymphoid tissues. Point mutations that disrupt the Zn(2+)-chelating ability of its amino-terminal RING finger domain abolished TRAC-1's ligase activity and the dominant inhibitory effect of C-terminal truncated TRAC-1 on TCR stimulation. The results of in vitro biochemical studies indicate that TRAC-1 can stimulate the formation of both K48- and K63-linked polyubiquitin chains and therefore could potentially activate both degradative and regulatory ubiquitin-dependent pathways. Antisense oligonucleotides to TRAC-1 specifically reduced TRAC-1 mRNA levels in Jurkat and primary T cells and inhibited their activation in response to TCR cross-linking. Collectively, these results indicate that the E3 ubiquitin ligase TRAC-1 functions as a positive regulator of T cell activation.
Zhao
Haoran
H
Rigel Pharmaceuticals, Inc., South San Francisco, CA 94080, USA. hzhao@rigel.com
Li
Connie C
CC
Pardo
Jorge
J
Chu
Peter C
PC
Liao
Charlene X
CX
Huang
Jianing
J
Dong
John G
JG
Zhou
Xiulan
X
Huang
Qi
Q
Huang
Betty
B
Bennett
Mark K
MK
Molineaux
Susan M
SM
Lu
Henry
H
Daniel-Issakani
Sarkiz
S
Payan
Donald G
DG
Masuda
Esteban S
ES
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001483:Base Sequence; D002384:Catalysis; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D002460:Cell Line; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology*; D008221:Lymphoid Tissue / Q000166:cytology / Q000201:enzymology / Q000276:immunology; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D056985:Nuclear Receptor Co-Repressor 2; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D025821:Polyubiquitin / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology*
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C539130:NCOR2 protein, human; D009687:Nuclear Proteins; D056985:Nuclear Receptor Co-Repressor 2; D010446:Peptide Fragments; D011948:Receptors, Antigen, T-Cell; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D025821:Polyubiquitin; C471610:UBC13 protein, S cerevisiae; C097310:UBE2D3 protein, human; C471624:UBE2V1 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases