Members of this family are nucleolar RNA-associated proteins (Nrap) which are highly conserved from yeast (Saccharomyces cerevisiae) to human. In the mouse, Nrap is ubiquitously expressed and is specifically localized in the nucleolus. Nrap is a large nucleolar protein (of more than 1000 amino acids). Nrap appears to be associated with ribosome biogenesis by interacting with pre-rRNA primary transcript. This domain has a nucleotidyltransferase structure.