DWNN is a ubiquitin like domain found at the N terminus of the RBBP6 family of splicing-associated proteins [1]. The DWNN domain is independently expressed in higher vertebrates so it may function as a novel ubiquitin-like modifier of other proteins [1].

1: DWNN, a novel ubiquitin-like domain, implicates RBBP6 in mRNA processing and ubiquitin-like pathways. Pugh DJ, Ab E, Faro A, Lutya PT, Hoffmann E, Rees DJ; BMC Struct Biol. 2006;6:1. PMID:16396680