The essential WD-repeat protein Rsa4p is required for rRNA processing and intra-nuclear transport of 60S ribosomal subunits.
We report the characterization of a novel factor, Rsa4p (Ycr072cp), which is essential for the synthesis of 60S ribosomal subunits. Rsa4p is a conserved WD-repeat protein that seems to localize in the nucleolus. In vivo depletion of Rsa4p results in a deficit of 60S ribosomal subunits and the appearance of half-mer polysomes. Northern hybridization and primer extension analyses of pre-rRNA and mature rRNAs show that depletion of Rsa4p leads to the accumulation of the 27S, 25.5S and 7S pre-rRNAs, resulting in a reduction of the mature 25S and 5.8S rRNAs. Pulse-chase analyses of pre-rRNA processing reveal that, at least, this is due to a strong delay in the maturation of 27S pre-rRNA intermediates to mature 25S rRNA. Furthermore, depletion of Rsa4p inhibited the release of the pre-60S ribosomal particles from the nucleolus to the nucleoplasm, as judged by the predominantly nucleolar accumulation of the large subunit Rpl25-eGFP reporter construct. We propose that Rsa4p associates early with pre-60S ribosomal particles and provides a platform of interaction for correct processing of rRNA precursors and nucleolar release of 60S ribosomal subunits.
de la Cruz
Jesús
J
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avda Reina Mercedes, 6 Apartado 1095, E-41012 Sevilla, Spain. jdlcd@us.es
Sanz-Martínez
Eloisa
E
Remacha
Miguel
M
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001692:Biological Transport; D002466:Cell Nucleolus / Q000737:chemistry / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D017124:Conserved Sequence; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D012322:RNA Precursors / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012335:RNA, Ribosomal / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*
D012322:RNA Precursors; D012335:RNA, Ribosomal; D012269:Ribosomal Proteins; C504806:Rsa4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins