Mechanism of ribosome stalling during translation of a poly(A) tail

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• Cells detect damaged messenger RNAs (mRNAs) through ribosome stalling during translation.
• Inappropriate polyadenylation within coding regions is a common eukaryotic mRNA defect.
• The mechanism of selective ribosome stalling upon encountering poly(A) sequences remains unclear.

Purpose of the Study:

• To elucidate the mechanism by which ribosomes selectively stall upon encountering polyadenylated sequences in mRNA.
• To understand how this stalling triggers cellular quality control pathways.

Main Methods:

• Biochemical approaches in mammalian systems.
• Structural analyses of ribosome-mRNA interactions.
• Investigating tRNA conformation and ribosome-tRNA clashes.

Main Results:

• Poly-lysine, encoded by poly(A), induces a suboptimal peptidyl-transfer RNA conformation.
• This conformation slows translation elongation, allowing poly(A) to form a helix in the decoding center.
• The altered decoding center obstructs incoming aminoacyl-tRNA, halting elongation.

Conclusions:

• Ribosomes selectively detect aberrant mRNAs via coincidence detection of poly-lysine and poly(A).
• This mechanism stalls translation elongation, initiating mRNA decay and protein quality control.
• This process is crucial for maintaining cellular homeostasis and preventing the accumulation of damaged proteins.