Different roles for two ubiquitin-like domains of ISG15 in protein modification.
ISG15 (interferon-stimulated gene 15) is a novel ubiquitin-like (UbL) modifier with two UbL domains in its architecture. We investigated different roles for the two UbL domains in protein modification by ISG15 (ISGylation) and the impact of Influenza B virus NS1 protein (NS1B) on regulation of the pathway. The results show that, although the C-terminal domain is sufficient to link ISG15 to UBE1L and UbcH8, the N-terminal domain is dispensable in the activation and transthiolation steps but required for efficient E3-mediated transfer of ISG15 from UbcH8 to its substrates. NS1B specifically binds to the N-terminal domain of ISG15 but does not affect ISG15 linkage via a thioester bond to its activating and conjugating enzymes. However, it does inhibit the formation of cellular ISG15 conjugates upon interferon treatment. We propose that the N-terminal UbL domain of ISG15 mainly functions in the ligation step and NS1B inhibits ISGylation by competing with E3 ligases for binding to the N-terminal domain.
Chang
Yong-Gang
YG
Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
Yan
Xian-Zhong
XZ
Xie
Yuan-Yuan
YY
Gao
Xue-Chao
XC
Song
Ai-Xin
AX
Zhang
Dong-Er
DE
Hu
Hong-Yu
HY
D000595:Amino Acid Sequence; D002460:Cell Line; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D013379:Substrate Specificity; D017186:Titrimetry; D044764:Ubiquitin-Activating Enzymes / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism; D014452:Ubiquitins / Q000235:genetics / Q000378:metabolism*; D017361:Viral Nonstructural Proteins / Q000378:metabolism
D016207:Cytokines; C085820:INS1 protein, influenza virus; D014452:Ubiquitins; D017361:Viral Nonstructural Proteins; C074034:ISG15 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D044764:Ubiquitin-Activating Enzymes