Abstract
The protein composition and structure of assembling 60S ribosomal subunits undergo numerous changes as pre-ribosomes transition from the nucleolus to the nucleoplasm. This includes stable anchoring of the Rpf2 subcomplex containing 5S rRNA, rpL5, rpL11, Rpf2 and Rrs1, which initially docks onto the flexible domain V of rRNA at earlier stages of assembly. In this work, we tested the function of the C-terminal domain (CTD) of Rpf2 during these anchoring steps, by truncating this extension and assaying effects on middle stages of subunit maturation. The rpf2Δ255-344 mutation affects proper folding of rRNA helices H68-70 during anchoring of the Rpf2 subcomplex. In addition, several assembly factors (AFs) are absent from pre-ribosomes or in altered conformations. Consequently, major remodeling events fail to occur: rotation of the 5S RNP, maturation of the peptidyl transferase center (PTC) and the nascent polypeptide exit tunnel (NPET), and export of assembling subunits to the cytoplasm.
Highlights
The protein composition and structure of assembling 60S ribosomal subunits undergo numerous changes as pre-ribosomes transition from the nucleolus to the nucleoplasm
Domains that form the convex solvent side of the subunit assemble first, followed by those that comprise the nascent polypeptide exit tunnel (NPET), and the central protuberance (CP) and the subunit interface containing the peptidyl transferase center (PTC)[8,9,10,11]
The C-terminal domain (CTD) of Rpf[2] is positioned between the GTPase domain of Nog[2] and ribosomal RNAs (rRNAs) helices H68-H71; it may contribute to maturation of these helices (Supplementary Fig. 2b)[27]
Summary
The protein composition and structure of assembling 60S ribosomal subunits undergo numerous changes as pre-ribosomes transition from the nucleolus to the nucleoplasm. This includes stable anchoring of the Rpf[2] subcomplex containing 5S rRNA, rpL5, rpL11, Rpf[2] and Rrs[1], which initially docks onto the flexible domain V of rRNA at earlier stages of assembly. Of 60S subunits is hierarchical; rRNA domains that form the convex solvent side of the subunit assemble first, followed by those that comprise the nascent polypeptide exit tunnel (NPET), and the central protuberance (CP) and the subunit interface containing the peptidyl transferase center (PTC)[8,9,10,11]. The 5S rRNA forms the 5S RNP complex with two r-proteins, rpL5 and rpL11, in the cytoplasm
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