The enzymes of the ubiquitylation pathway play a pivotal role in a number of cellular processes including regulated and targeted proteasomal degradation of substrate proteins. Three classes of enzymes are involved in the process of ubiquitination; activating enzymes (E1s), conjugating enzymes (E2s) and protein ligases (E3s). UBE2L6 is a member of the E2 conjugating enzyme family, identification and cloning of the gene from a yeast 2 hybrid screen was first described by Kumar et al. (1997). Human UBE2L6 has been mapped to chromosome 11q12 and shares 46% homology with UBE2L3 (Recombinant UBE2L6 forms thiol ester complexes with ubiquitin in vitro and is able to transfer ubiquitin to E6AP (Ardley et al., 2000). UBE2L6 has also been shown to conjugate the ubiquitin like protein (Ubl) ISG15. In vitro assays and RNA interference have shown that of the ubiquitin E2 enzymes tested UBE2L6 is a major E2 enzyme for ISG15 conjugation (Li et al., 2006; Zhao et al., 2004). The nuclear matrix protein Msx2-interacting nuclear target protein (MINT) regulates the expression of key transcriptional effectors in diverse signalling pathways and has been identified as a binding partner of UBE2L6 by co-immunoprecipitation and GST pull down (Li et al., 2006). Degradation of the chromosomal translocation products AML1-ETO and PML-RAR alpha which contribute to the pathogenesis of leukaemias is mediated by the E2 enzyme UBE2L6 and the E3 ligase SIAH-1. Thus, UBE2L6 could be a potential therapeutic target in the treatment of leukaemia (Kramer et al., 2008).
Ardley HC, Rose SA, Tan N, Leek JP, Markham AF, Robinson PA (2000) Genomic organization of the human ubiquitin-conjugating enzyme gene, UBE2L6 on chromosome 11q12. Cytogenet Cell Genet 89, 137-40.
Kramer OH, Muller S, Buchwald M, Reichardt S, Heinzel T (2008) Mechanism for ubiquitylation of the leukemia fusion proteins AML1-ETO and PML-RARalpha. FASEB J 22, 1369-79.
Kumar S, Kao WH, Howley PM (1997) Physical interaction between specific E2 and Hect E3 enzymes determines functional cooperativity. J Biol Chem 272, 13548-54.
Li J, Wang J, Yang X, Qin H, Dong X, Zhu Y, Liang L, Liang Y, Han H (2006) The Spen homolog Msx2-interacting nuclear target protein interacts with the E2 ubiquitin-conjugating enzyme UbcH8. Mol Cell Biochem 288, 151-7.
Zhao C, Beaudenon SL, Kelley ML, Waddell MB, Yuan W, Schulman BA, Huibregtse JM, Krug RM (2004) The UbcH8 ubiquitin E2 enzyme is also the E2 enzyme for ISG15, an IFN-alpha/beta-induced ubiquitin-like protein. Proc Natl Acad Sci U S A 101, 7578-82.