Mechanism of Ribosome Stalling by the AMD1 C-terminal Tail Arrest Peptide

Area of Science:

• Molecular Biology
• Structural Biology
• Gene Regulation

Background:

• Adenosylmethionine decarboxylase 1 (AMD1) is crucial for polyamine biosynthesis.
• A conserved C-terminal extension (C-tail) in AMD1 is known to cause ribosome stalling after stop codon readthrough.
• The precise molecular mechanism of this C-tail-mediated ribosome stalling remains elusive.

Purpose of the Study:

• To elucidate the structural basis of ribosome stalling induced by the AMD1 C-tail.
• To understand how the C-tail interacts with translation termination factors.
• To investigate the broader implications of this regulatory mechanism in gene expression.

Main Methods:

• Determined the structure of the ribosome-nascent chain complex paused by the AMD1 C-tail.
• Utilized cryo-electron microscopy to visualize the interaction between the ribosome, nascent chain, and termination factors.
• Analyzed ribosome profiling data to identify other genes exhibiting similar regulatory patterns.

Main Results:

• The AMD1 C-tail forms a molecular clamp that obstructs the peptidyl-transferase center.
• This clamp prevents the accommodation of the eukaryotic release factor 1 (eRF1) GGQ motif, halting translation termination.
• Identified other genes with similar stop codon readthrough and ribosome stalling patterns, indicating a conserved regulatory mechanism.

Conclusions:

• The AMD1 C-tail employs a unique structural mechanism to stall ribosomes, regulating gene expression.
• This mechanism involves direct interference with the translation termination process.
• Regulatory readthrough-stall mechanisms may be a more widespread phenomenon in vertebrate gene regulation than previously thought.