Unresolved stalled ribosome complexes restrict cell-cycle progression after genotoxic stress

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Ribosome-associated quality control is crucial for cellular health.
• The ASC-1 complex (ASCC) is known to disassemble stalled ribosomes.
• Understanding differential ribosome stalling is key to cellular stress responses.

Purpose of the Study:

• To investigate the differential resolution of stalled ribosomes by the ASCC.
• To determine the impact of ASCC-refractory stalled ribosomes on cellular processes.
• To elucidate the role of ribosome stalling in cell-cycle regulation and stress response.

Main Methods:

• Utilized human cell lines to study ribosome stalling.
• Employed translation elongation inhibitors and mRNA modifications (methylation).
• Induced DNA damage using UV light and 4-nitroquinoline 1-oxide (4NQO).
• Investigated ASCC recruitment and activity.
• Analyzed cell-cycle arrest via ZAK-p38^MAPK signaling.

Main Results:

• Identified two distinct classes of stalled ribosomes based on ASCC sensitivity.
• Ribosomes stalled by inhibitors or methylated mRNA are rapidly resolved by ASCC.
• UV- and 4NQO-induced stalled ribosomes are refractory to ASCC-mediated resolution.
• Unresolved stalled ribosomes persist in cells.
• Ribosome stalling activates cell-cycle arrest, prolonged by ASCC-refractory stalls.

Conclusions:

• The sensitivity of stalled ribosomes to the ASCC dictates their resolution kinetics.
• ASCC-refractory stalled ribosomes contribute to prolonged cell-cycle delay.
• Differential ribosome stalling resolution influences the adaptive cellular stress response.