Poster abstracts
Poster number 136 submitted by Amber LaPeruta
The GTPase activity of the ribosome assembly factor Nog1 is required for its release from the large ribosomal subunit
Amber J. LaPeruta (Carnegie Mellon University), Dan M. Wilson (Carnegie Mellon University), John L. Woolford (Carnegie Mellon University), Vikram Panse (ETH Zurich)
Abstract:
Efficient and accurate protein synthesis requires proper assembly of ribosomal functional centers. Defective ribosome assembly disrupts protein homeostasis and causes ribosomopathies and cancer. One essential functional center, the peptidyl transferase center (PTC), regulates protein synthesis. Mechanisms involved in PTC assembly have remained elusive due to lack of structural data. However, recent advances in cryo-EM technology enabled us to visualize the Nog2-TAP, Arx1-TAP and Nmd3-TAP pre-60S structures, an unprecedented feat. These structures informed hypotheses regarding PTC construction. The Nog2-TAP structure shows that the essential assembly factor Nog1 probes the rRNA of the PTC with its N-terminal helix bundle domain. Adjacent to the helix bundle, Nog1 has an Obg-like GTPase domain whose function in ribosome assembly remains unknown. To give mechanistic insight into PTC assembly, we are assessing ribosome biogenesis defects that result from the nog1G223A mutation in the GTPase domain of Nog1. In murine cell lines, the analogous mutation is a dominant lethal mutation that causes early, 27SB pre-rRNA processing defects. Using northern blot analysis, affinity purification of assembly intermediates and western blot analysis, we show that the GTPase activity of Nog1 is essential for its release from the large ribosomal subunit during assembly. We hypothesize GTP hydrolysis creates structural rearrangements in Nog1 that remove the helix bundle of Nog1 from the PTC to allow the release of Nog1.
Keywords: Ribosome, GTPase, Large Subunit