Sde2 (silencing defective 2) is a ubiquitin-fold-containing splicing regulator that supports splicing of selected pre-mRNAs in an intron-specific manner in Schizosaccharomyces pombe. Both fission yeast and human Sde2 are translated as inactive precursor proteins harbouring the ubiquitin-fold domain linked through an invariant GGKGG motif to a C-terminal domain. The Sde2 protein has a ubiquitin-fold at its N-terminus, which must be cleaved by the ubiquitin-specific proteases (USPs) Ubp5 and Ubp15. After cleavage, the C-terminal domain of Sde2, which starts with a lysine, gets incorporated into the spliceosome [1]. This entry represents the ubiquitin fold N-terminal domain found in Sde2 proteins.

1: Sde2 is an intron-specific pre-mRNA splicing regulator activated by ubiquitin-like processing. Thakran P, Pandit PA, Datta S, Kolathur KK, Pleiss JA, Mishra SK; EMBO J. 2018;37:89-101. PMID:28947618