The assembly of protein–RNA complexes (ribonucleoproteins; RNPs) is one of the most fundamental processes of all life forms, underlying transcription, translation, and splicing. Errors in RNP assembly underlie many human diseases. The formation of an RNP complex involves synthesis and correct folding of the individual protein and nucleic acid components and specific intermolecular interactions between them. A major barrier to understanding RNP assembly has been the reliance on in vitro studies based on preformed RNA and protein molecules, whereas in cells many such complexes form on the nascent RNA while it is emerging from the RNA polymerase. Furthermore, our understanding is heavily based on compositional and structural knowledge of the mature RNPs, but we are lacking structural and, importantly, dynamic information on transient biochemically unstable assembly intermediates, which are required for a full quantitative description of the assembly processes.
We are studying the molecular mechanisms by which various RNPs assemble, and in particular are establishing how their assembly is coupled to transcription and folding of the RNA and how it is affected by other cellular factors (Fig. 1). We focus on bacterial ribosome assembly (e.g. Duss et al., Cell 2019) and on the coupling between mRNA transcription and translation (e.g. Duss et al., Nature 2014), in E. coli and the human pathogen Mycobacterium tuberculosis. Efforts are also directed towards understanding eukaryotic RNP assemblies. By using single-molecule methods we can directly watch how single protein–RNA complexes assemble in real time (Fig. 2). By combining this with high-resolution structural information on assembly intermediates, we obtain a full molecular understanding of how protein–RNA complexes are formed and how their assembly is regulated. This understanding gives us new opportunities to interfere with RNP assembly to fight a variety of diseases and to create new functional assemblies for synthetic biology.