Ribosomal processing requires a series of endo- and exonucleolytic steps for the production of mature ribosomes, of which most have been described. To ensure ribosome synthesis, 3′ end formation of rRNA uses multiple nucleases acting in parallel; however, a similar parallel mechanism had not been described for 5′ end maturation. Here, we identify Rrp17p as a previously unidentified 5′-3′ exonuclease essential for ribosome biogenesis, functioning with Rat1p in a parallel processing pathway analogous to that of 3′ end formation. Rrp17p is required for efficient exonuclease digestion of the mature 5′ ends of 5.8SS and 25S rRNAs, contains a catalytic domain close to its N terminus, and is highly conserved among higher eukaryotes, being a member of a family of exonucleases. We show that Rrp17p binds late pre-60S ribosomes, accompanying them from the nucleolus to the nuclear periphery, and provide evidence for physical and functional links between late 60S subunit processing and export. © 2009 Elsevier Inc. All rights reserved.
Oeffinger, M., Zenklusen, D., Ferguson, A., Wei, K. E., El Hage, A., Tollervey, D., … Rout, M. P. (2009). Rrp17p is a eukaryotic exonuclease required for 5’ end processing of Pre-60S ribosomal RNA. Molecular Cell, 36(5), 768–81. https://doi.org/10.1016/j.molcel.2009.11.011