Restricted expression and subnuclear localization of the Drosophila gene Dnop5, a member of the Nop/Sik family of the conserved rRNA processing factors.

Members of the conserved nop5/sik1 gene family encode components of small nucleolar ribonucleoprotein (snoRNP) complexes, which have an essential function in rRNA-processing. We describe a novel Drosophila member of this family, termed Dnop5. The gene is expressed in nurse cells during oogenesis and transcripts are deposited into the growing oocyte. Maternal transcripts become evenly distributed in the egg and remain in a ubiquitous pattern during early embryogenesis. Zygotic Dnop5 expression is initiated during the extended germband stage. Transcripts accumulate in mesoderm and midgut primordia, and in the developing imaginal discs of the larvae. Consistent with a function in rRNA processing, Dnop5 protein (DNop5) accumulates in a nuclear substructure, likely to be the nucleolus. Maternal protein accumulates in the nucleolus of all cells in the early embryo, whereas DNop5 that is derived from zygotic mRNA, is restricted to the nuclei of muscles and midgut.