H/ACA snR30 snoRNP guides independent 18S rRNA subdomain formation – Dataset 4

Ribosome biogenesis follows a hierarchical set of pre-ribosomal RNA (pre-RNA) folding and processing steps. The earliest, biochemically stable pre-ribosome is the 90S particle, which is assembled co-transcriptionally in the nucleolus. It is unclear how pre-rRNA, ribosomal proteins and assembly factors play together in the early stages of 90S maturation. Is has remained unclear, how the numerous snoRNAs, which guide pre-rRNA modification and folding while the nascent rRNA is flexible and hence accessible, are involved in pre-ribosomal maturation. Here, we identify the conserved C-terminus of assembly factor Krr1 as crucial for efficient release of the essential snR30. Furthermore, we show that snR30 is bound to the central domain of the 18S rRNA within a complex that contains assembly factors and ribosomal proteins. Our study shows how independent 18S domain maturation is guided by snR30 in coupling rRNA chaperoning with the delivery of ribosomal proteins.