Interaction network of the ribosome assembly machinery from a eukaryotic thermophile
Authors: Baßler J, Ahmed YL, Kallas M, Kornprobst M, Calviño FR, Gnädig M, Thoms M, Stier G, Ismail S, Kharde S, Castillo N, Griesel S, Bastuck S, Bradatsch B, Thomson E, Flemming D, Sinning I, Hurt E
CellNetworks People: Hurt Ed, Sinning Irmgard
Journal: Protein Sci. 2017 Feb;26(2):327-342. doi: 10.1002/pro.3085.

Ribosome biogenesis in eukaryotic cells is a highly dynamic and complex process innately linked to cell proliferation. The assembly of ribosomes is driven by a myriad of biogenesis factors that shape pre-ribosomal particles by processing and folding the ribosomal RNA and incorporating ribosomal proteins. Biochemical approaches allowed the isolation and characterization of pre-ribosomal particles from Saccharomyces cerevisiae, which lead to a spatiotemporal map of biogenesis intermediates along the path from the nucleolus to the cytoplasm. Here, we cloned almost the entire set (∼180) of ribosome biogenesis factors from the thermophilic fungus Chaetomium thermophilum in order to perform an in-depth analysis of their protein-protein interaction network as well as exploring the suitability of these thermostable proteins for structural studies. First, we performed a systematic screen, testing about 80 factors for crystallization and structure determination. Next, we performed a yeast 2-hybrid analysis and tested about 32,000 binary combinations, which identified more than 1000 protein-protein contacts between the thermophilic ribosome assembly factors. To exemplary verify several of these interactions, we performed biochemical reconstitution with the focus on the interaction network between 90S pre-ribosome factors forming the ctUTP-A and ctUTP-B modules, and the Brix-domain containing assembly factors of the pre-60S subunit. Our work provides a rich resource for biochemical reconstitution and structural analyses of the conserved ribosome assembly machinery from a eukaryotic thermophile.