minifly, a Drosophila gene required for ribosome biogenesis

We report here the genetic, molecular, and functional characterization of t he Drosophila melanogaster minifly (mfl) gene. Genetic analysis shows that mfl is essential for Drosophila viability and fertility. While P-element in duced total loss-of-function mutations cause lethality, mfl partial loss-of -function mutations cause pleiotropic defects, such as extreme reduction of body size, developmental delay, hatched abdominal cuticle, and reduced fem ale fertility. Morphological abnormalities characteristic of apoptosis are found in the ovaries, and a proportion of eggs laid by mfl mutant females d egenerates during embryogenesis. We show that mfl encodes an ubiquitous nuc leolar protein that plays a central role in ribosomal RNA processing and ps eudouridylation, whose known eukaryotic homologues are yeast Cfb5p, rat NAP 57 and human dyskerin, encoded by the gene responsible for the X-linked dys keratosis congenita disease. mfl genetic analysis represents the first in v ivo functional characterization of a member of this highly conserved gene f amily from higher eukaryotes. In addition, we report that mfl hosts an intr on encoded box H/ACA snoRNA gene, the first member of this class of snoRNAs identified so far from Drosophila.