Yeast ribosomal protein L7 and its homologue Rlp7 are simultaneously present at distinct sites on pre-60S ribosomal particles.
Ribosome biogenesis requires >300 assembly factors in Saccharomyces cerevisiae. Ribosome assembly factors Imp3, Mrt4, Rlp7 and Rlp24 have sequence similarity to ribosomal proteins S9, P0, L7 and L24, suggesting that these pre-ribosomal factors could be placeholders that prevent premature assembly of the corresponding ribosomal proteins to nascent ribosomes. However, we found L7 to be a highly specific component of Rlp7-associated complexes, revealing that the two proteins can bind simultaneously to pre-ribosomal particles. Cross-linking and cDNA analysis experiments showed that Rlp7 binds to the ITS2 region of 27S pre-rRNAs, at two sites, in helix III and in a region adjacent to the pre-rRNA processing sites C1 and E. However, L7 binds to mature 25S and 5S rRNAs and cross-linked predominantly to helix ES7(L)b within 25S rRNA. Thus, despite their predicted structural similarity, our data show that Rlp7 and L7 clearly bind at different positions on the same pre-60S particles. Our results also suggest that Rlp7 facilitates the formation of the hairpin structure of ITS2 during 60S ribosomal subunit maturation.
Departamento de Genética, Universidad de Sevilla, E-41012 Seville, Spain, Institut Pasteur, Génétique des Interactions Macromoléculaires, CNRS UMR-3525, Paris, France and Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Seville, Spain.
Reyes
R
Babiano
Gwenael
G
Badis
Cosmin
C
Saveanu
Abdelkader
A
Namane
Antonia
A
Doyen
Antonio
A
Díaz-Quintana
Alain
A
Jacquier
Micheline
M
Fromont-Racine
Jesús
J
de la Cruz
D001483:Base Sequence; D001665:Binding Sites; D008969:Molecular Sequence Data; D012322:RNA Precursors / Q000737:chemistry / Q000378:metabolism; D012335:RNA, Ribosomal / Q000737:chemistry / Q000378:metabolism*; D012341:RNA, Ribosomal, 5S / Q000737:chemistry / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D054683:Ribosome Subunits, Large, Eukaryotic / Q000737:chemistry; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
C084787:RLP7 protein, S cerevisiae; D012322:RNA Precursors; D012335:RNA, Ribosomal; D012341:RNA, Ribosomal, 5S; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; C065039:RNA, ribosomal, 25S; C073617:RPL7A protein, S cerevisiae