Poster abstracts

Poster number 32 submitted by Luke Diorio-Toth

Recruiting of ribosomal proteins by ribosomal assembly factors

Michael Gamalinda (Carnegie Mellon University, Department of Biological Sciences), Luke Diorio-Toth (Carnegie Mellon University, Department of Biological Sciences), John L Woolford (Carnegie Mellon University, Department of Biological Sciences)

Abstract:
Ribosome biogenesis is a complex, multistep process that involves processing and folding of rRNA and binding of ribosomal proteins. Previous research has shown that many different classes of trans-acting proteins are also required for assembly, with both enzymatic and structural functions. However, the precise functions of most of these assembly factors are not known. To begin to explore roles of assembly factors in ribosome biogenesis, we investigated their functional relationships with ribosomal proteins. Although a significant amount of information exists about roles of both ribosomal proteins and assembly factors in ribosome biogenesis, not much is known about the interplay between the two types of proteins. Previous research has shown order of assembly of ribosomal proteins into pre-ribosomes, as well as with which assembly factors they associate. However, most of these studies started with specific ribosomal proteins and then asked: with which assembly factors do they interact, and which assembly factors depend on them to associate with pre-ribosomes?
Specifically, we asked which ribosomal proteins depend upon the assembly factors Nog1, Nog2, Dbp10, and Spb4 to assemble. These assembly factors were selected because they are thought to have similar functions (as GTPases or ATPases). Ribosomal proteins were tagged in strains conditional for expression of these assembly factors, and association of ribosomal proteins with pre-ribosomes was explored upon depletion of each of these factors. This work is intended to complement the work that has already been done by providing a more complete picture of how these ribosomal proteins fit into the established recruitment pathway for assembly factors. Because there is much more structural information about position and conformation of ribosomal proteins on the pre-ribosome, this work will hopefully elucidate similar information about the assembly factors. This approach has benefitted us because we have reevaluated out the previously established assembly hierarchy. This work has also lead us to believe that it is not simply RNA processing that allows these ribosomal proteins to stably associate with the pre-ribosome, but the presence of these assembly factors is required prior to the processing of RNA.

Keywords: ribosome assembly, ribosomal proteins, ribosome assembly factors