Special Seminar: Biochemistry Division
Seminar title: "Nascent ribosome assembly in real-time"
Abstract Seminar:
The ribosomes are the cellular protein production machines. Their assembly is an efficient, but complex and heterogeneous process during which ribosomal proteins assemble on the nascent ribosomal RNA (rRNA) directly emerging from the RNA polymerase. Understanding how the interplay between nascent RNA folding and protein binding determines the fate of transcripts remains a major challenge. We have developed a single-molecule fluorescence-microscopy approach for simultaneous tracking of transcription, nascent RNA folding and the assembly of proteins on the nascent transcript (Duss et al., Nat Comm, 2018; Duss et al., Cell, 2019). We use this approach to follow assembly of the entire 3’domain of the bacterial small ribosomal subunit in real-time. We find that co-transcriptional rRNA folding is complicated by the formation of long-range RNA interactions, and that r-proteins self-chaperone the rRNA folding process prior to stable incorporation into a ribonucleoprotein complex (RNP). Assembly is initiated by transient rather than stable protein binding, and the protein-RNA binding dynamics gradually decrease during assembly. This work questions the paradigm of strictly sequential and cooperative ribosome assembly and suggests that transient binding of RNA binding proteins to cellular RNAs could provide a general mechanism to shape nascent RNA folding during RNP assembly.
