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 n ucleolar ribonucleoprotein (snoRNP) complexes, which have an essential func tion in rRNA-processing. We describe a novel Drosophila member of this fami ly, termed Dnop5. The gene is expressed in nurse cells during oogenesis and transcripts are deposited into the growing oocyte. Maternal transcripts be come evenly distributed in the egg and remain in a ubiquitous pattern durin g early embryogenesis. Zygotic Dnop5, expression is initialed during the ex tended germband stage. Transcripts accumulate in mesoderm and midgut primor dia, and in the developing imaginal discs of the larvae. Consistent with a function in rRNA processing, Dnop5 protein (DNopS) accumulates in a nuclear substructure, likely to be the nucleolus. Maternal protein accumulates in the nucleolus of all cells in the early embryo, whereas DNopS that is deriv ed from zygotic mRNA, is restricted to the nuclei of muscles and midgut. (C ) 2000 Elsevier Science Ireland Ltd. All rights reserved.