The enzymes of the ISGylation pathway play a pivotal role in the immnune response. Three classes of enzymes are involved in the process of ISGylation an activating enzyme (E1), conjugating enzymes (E2s) and protein ligases (E3s). UBA7 is a member of the E1 activating enzyme family and cloning of the human gene was first described by Kok et al. (1993). The UBA7 gene has been mapped to chromosome 3p21 by high resolution fluorescence in situ hybridization (Carritt et al. 1992). UBA7 and UBE2L6 have been reported to function as the E1 and E2 enzymes respectively for ISG conjugation forming a thioester intermediate through Cys-131 of UBE2L6 (Takeuchi et al. 2005). UBA7 (Ube1L) knockout (KO) mice are deficient in ISGylation and are fertile with no obvious phenotype. (Kim et al. 2006). The expression of UBA7 was found to be reduced in many lung cancer cell lines and although originally thought to be a tumor suppressor gene candidate recent studies have demonstrated that UBA7 does not suppress the development of lung adenoma or thymic lymphoma in a K-rasLA2 cancer model (Kok et al. 1993).
Carritt B, Kok K, van den Berg A, Osinga J, Pilz A, et al. (1992) A gene from human chromosome region 3p21 with reduced expression in small cell lung cancer. Cancer Res 52, 1536-1541.
Kim KI, Yan M, Malakhova O, Luo JK, Shen MF, et al. (2006) Ube1L and protein ISGylation are not essential for alpha/beta interferon signaling. Mol Cell Biol 26, 472-479.
Kok K, Hofstra R, Pilz A, van den Berg A, Terpstra P, et al. (1993) A gene in the chromosomal region 3p21 with greatly reduced expression in lung cancer is similar to the gene for ubiquitin-activating enzyme. Proc Natl Acad Sci USA 90, 6071-6075.
Takeuchi T, Iwahara S, Saeki Y, Sasajima H, Yokosawa H (2005) Link between the ubiquitin conjugation system and the ISG15 conjugation system: ISG15 conjugation to the UbcH6 ubiquitin E2 enzyme. J Biochem 138, 711-719.