The ~75-residue DWNN (Domain With No Name) domain is highly conserved through eukaryotic species but is absent in prokaryotes. The DWNN domain is found only at the N terminus of the RBBP6 family of proteins which includes:

• Mammalian RBBP6, a splicing-associated protein that plays a role in the induction of apoptosis and regulation of the cell cycle.
• Drosophila melanogaster … expand

The ~75-residue DWNN (Domain With No Name) domain is highly conserved through eukaryotic species but is absent in prokaryotes. The DWNN domain is found only at the N terminus of the RBBP6 family of proteins which includes:

• Mammalian RBBP6, a splicing-associated protein that plays a role in the induction of apoptosis and regulation of the cell cycle.
• Drosophila melanogaster (Fruit fly) SNAMA (something that sticks like glue), a protein that appears to play a role in apoptosis.

All of the identified RBBP6 homologues include the DWNN domain, a CCHC-type zinc finger and a RING-type zinc finger. The three domain form is found in plants, protozoa, fungi and microsporidia. The RBBP6 homologues in vertebrates, insects and worms are longer and include additional domains. In addition to forming part of the full-length RBBP6 protein, the DWNN domain is also expressed in vertebrates as a small protein containing a DWNN domain and a short C-terminal tail (RBBP6 variant 3). The DWNN domain adopts a fold similar to the ubiquitin one, characterised by two α-helices and four β-sheets ordered as β-β-α-β-α-β along the sequence. The similarity of DWNN domain to ubiquitin and the presence of the RING finger suggest that the DWNN domain may act as an ubiquitin-like modifier, possibly playing a role in the regulation of the splicing machinery [ PUBMED:15733535 PUBMED:16396680 ].