Non-coding RNA biogenesis in higher eukaryotes has not been fully characterized. Here, we studied the Drosophila melanogaster Rexo5 (CG8368) protein, a metazoan-specific member of the DEDDh 3′-5′ single-stranded RNA exonucleases, by genetic, biochemical, and RNA-sequencing approaches. Rexo5 is required for small nucleolar RNA (snoRNA) and rRNA biogenesis and is essential in D. melanogaster. Loss-of-function mutants accumulate improperly 3′ end-trimmed 28S rRNA, 5S rRNA, and snoRNA precursors in vivo. Rexo5 is ubiquitously expressed at low levels in somatic metazoan cells but extremely elevated in male and female germ cells. Loss of Rexo5 leads to increased nucleolar size, genomic instability, defective ribosome subunit export, and larval death. Loss of germline expression compromises gonadal growth and meiotic entry during germline development. Gerstberger et al. adapt hydrolysis-based small RNA-sequencing to identify RNA targets of the conserved 3′-5′ RNA exonuclease Rexo5 in Drosophila melanogaster. Rexo5 was revealed as a key factor in snoRNA, 28S rRNA, and 5S rRNA 3′ end maturation. Loss of function of Rexo5 leads to impaired ribosomal export and germline developmental defects.
Gerstberger, S., Meyer, C., Benjamin-Hong, S., Rodriguez, J., Briskin, D., Bognanni, C., … Tuschl, T. (2017). The Conserved RNA Exonuclease Rexo5 Is Required for 3′ End Maturation of 28S rRNA, 5S rRNA, and snoRNAs. Cell Reports, 21(3), 758–772. https://doi.org/10.1016/j.celrep.2017.09.067