Three Brachypodium distachyon Ueva1s Promote Ubc13-Mediated Lys63-Linked Polyubiquitination and Confer Different Functions

In this study, we report the identification and functional characterization of three Brachypodium distachyon UEV genes. All three BdUev1 s form heterodimers with BdUbcl3s, which are capable of catalyzing Lys63-linked polyubiquitination in vitro. The three BdUEV1 genes are also able to functionally complement the budding yeast rnms2 mutant defective in DNA-damage tolerance. BdUev1A differs from the other two BdUev1 s in that it contains an 18-amino acid tail, which appears to compromise its function in yeast, as deletion of this tail restores full function. BdUevl A is excluded from the nucleus, whereas BdUevl B, BdUevl C and the C-terminally truncated BdUev1A are mainly found in the nucleus. These and the BdUEV1 gene expression analysis allow us to speculate that although all three BdUev 1 s function by promoting Lys63-linked polyubiquitination, BdUev1B and BdUev1C are involved in DNA-damage response and possibly other nuclear functions, while BdUevl A is required for non-nuclear function(s).