biostudies-literatureHamze HInstitut National du CancerCIOES OrganizationSwiss National Science FoundationCNRSAgence Nationale de la RechercheLa Ligue Nationale Contre Le CancerLebanese UniversityToulouse Universitygkaf134https://www.ebi.ac.uk/biostudies/studies/S-EPMC11879421biostudies-literatureUnknown53(5)The early steps of large-ribosomal-subunit assembly feature among the least understood steps of ribosome synthesis in eukaryotes. In Saccharomyces cerevisiae, the box C/D chaperone small nucleolar ribonucleoprotein (snoRNP) snR190 and the Npa1 complex, composed of the α-solenoid scaffold proteins Npa1 and Npa2, the DEAD-box helicase Dbp6, the RNA-binding protein Nop8, and Rsa3, are likely involved in early 25S ribosomal RNA (rRNA) folding events. Here, we report for the first time the existence outside pre-ribosomal particles of an independent macromolecular assembly constituted by the Npa1 complex and the chaperone snoRNP snR190. Nop8 mediates the formation of this assembly and can associate on its own with free snR190 snoRNP. Moreover, Nop8 RNA Recognition Motif (RRM) helps tether the snNucleic acids researchThe snoRNP chaperone snR190 and the Npa1 complex form a macromolecular assembly required for 60S ribosomal subunit maturation.PMC11879421PLBIO-2020-091ANR-20-CE12-0026310030_204801ANR-21-CE12-0008-01Kressler DHenras AKMendez-Godoy AHenry YBourdeaux JSanto PEHamze HHumbert ODominique CJaafar MKhreiss APlisson-Chastang CAlbert BfalseThe snoRNP chaperone snR190 and the Npa1 complex form a macromolecular assembly required for 60S ribosomal subunit maturation.The early steps of large-ribosomal-subunit assembly feature among the least understood steps of ribosome synthesis in eukaryotes. In Saccharomyces cerevisiae, the box C/D chaperone small nucleolar ribonucleoprotein (snoRNP) snR190 and the Npa1 complex, composed of the α-solenoid scaffold proteins Npa1 and Npa2, the DEAD-box helicase Dbp6, the RNA-binding protein Nop8, and Rsa3, are likely involved in early 25S ribosomal RNA (rRNA) folding events. Here, we report for the first time the existence outside pre-ribosomal particles of an independent macromolecular assembly constituted by the Npa1 complex and the chaperone snoRNP snR190. Nop8 mediates the formation of this assembly and can associate on its own with free snR190 snoRNP. Moreover, Nop8 RNA Recognition Motif (RRM) helps tether the sn2025-01-01T00:00:00Z2025 Feb2025-04-19T17:32:32.235Z2025-04-19T17:32:32.235ZS-EPMC118794214003770510.1093/nar/gkaf134