Functional Redundancy of Yeast Proteins Reh1 and Rei1 in Cytoplasmic 60S Subunit Maturation

Abstract

The biogenesis of the large (60S) ribosomal subunit in eukaryotes involves nucleolar, nucleoplasmic, and cytoplasmic steps. The cytoplasmic protein Rei1, found in all eukaryotes, was previously shown to be necessary for the nuclear reimport of 60S subunit export factor Arx1. In this study we investigate the function of Reh1, a protein with high sequence similarity to Rei1. We demonstrate an overlapping function for Reh1 and Rei1 in the cytoplasmic maturation of the 60S subunit that is independent of Arx1 recycling. We observe that strains lacking both Reh1 and Rei1 accumulate salt-labile 60S subunits, suggesting that Reh1/Rei1 is necessary for the cytoplasmic 60S subunit to adopt its mature, stable form.

ACKNOWLEDGMENTS

We are grateful to Jonathan Warner (Albert Einstein Medical School, Bronx, NY) for anti-Rpl3 antibody; Bernard Trumpower (Dartmouth Medical School, Hanover, NH) for anti-Rpl10 antibody and the DEH221+ strain; Micheline Fromont-Racine (Pasteur Institute, Paris, France) for anti-Arx1, anti-Rei1, and anti-Rlp24 antibodies and the LMA374 strain; Arlen Johnson (University of Texas, Austin, TX) for anti-Nmd3 antibody and pAJ1004 and pAJ1015 plasmids; Franco Fasiolo (IBMC, Strasbourg, France) for anti-TIF6 antibody; and Heather Hundley for critical reading of the manuscript.

This research was supported by the National Institutes of Health (NRSA postdoctoral fellowship to K.M.P.). B.L.B. is a Howard Hughes Medical Institute Investigator.