5nt1

Structural highlights

Function

[TRI25_HUMAN] Functions as a ubiquitin E3 ligase and as an ISG15 E3 ligase. Involved in innate immune defense against viruses by mediating ubiquitination of DDX58. Mediates 'Lys-63'-linked polyubiquitination of the DDX58 N-terminal CARD-like region which is crucial for triggering the cytosolic signal transduction that leads to the production of interferons in response to viral infection. Promotes ISGylation of 14-3-3 sigma (SFN), an adapter protein implicated in the regulation of a large spectrum signaling pathway. Mediates estrogen action in various target organs.^{[1] [2] [3]} [NS1_I34A1] Inhibits post-transcriptional processing of cellular pre-mRNA, by binding and inhibiting two cellular proteins that are required for the 3'-end processing of cellular pre-mRNAs: the 30 kDa cleavage and polyadenylation specificity factor (CPSF4) and the poly(A)-binding protein 2 (PABPN1). This results in the accumulation of unprocessed 3' end pre-mRNAs which can't be exported from the nucleus. Cellular protein synthesis is thereby shut off very early after virus infection. Viral protein synthesis is not affected by the inhibition of the cellular 3' end processing machinery because the poly(A) tails of viral mRNAs are produced by the viral polymerase through a stuttering mechanism (By similarity). Prevents the establishment of the cellular antiviral state by inhibiting TRIM25-mediated DDX58 ubiquitination, which normally triggers the antiviral transduction signal that leads to the activation of type I IFN genes by transcription factors like IRF3 and IRF7. Prevents human EIF2AK2/PKR activation, either by binding double-strand RNA, or by interacting directly with EIF2AK2/PKR. This function may be important at the very beginning of the infection, when NS1 is mainly present in the cytoplasm. Also binds poly(A) and U6 snRNA. Suppresses the RNA silencing-based antiviral response in Drosophila cells (By similarity).

References

1. ↑ Zou W, Zhang DE. The interferon-inducible ubiquitin-protein isopeptide ligase (E3) EFP also functions as an ISG15 E3 ligase. J Biol Chem. 2006 Feb 17;281(7):3989-94. Epub 2005 Dec 13. PMID:16352599 doi:http://dx.doi.org/10.1074/jbc.M510787200
2. ↑ Nakasato N, Ikeda K, Urano T, Horie-Inoue K, Takeda S, Inoue S. A ubiquitin E3 ligase Efp is up-regulated by interferons and conjugated with ISG15. Biochem Biophys Res Commun. 2006 Dec 15;351(2):540-6. Epub 2006 Oct 18. PMID:17069755 doi:http://dx.doi.org/10.1016/j.bbrc.2006.10.061
3. ↑ Gack MU, Shin YC, Joo CH, Urano T, Liang C, Sun L, Takeuchi O, Akira S, Chen Z, Inoue S, Jung JU. TRIM25 RING-finger E3 ubiquitin ligase is essential for RIG-I-mediated antiviral activity. Nature. 2007 Apr 19;446(7138):916-920. PMID:17392790 doi:http://dx.doi.org/10.1038/nature05732