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The ASC-1 Complex Disassembles Collided Ribosomes

Szymon Juszkiewicz1, Shaun H Speldewinde2, Li Wan2

  • 1MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK.

Molecular Cell
|June 25, 2020
PubMed

Insights

The ASC-1 complex (ASCC) disassembles stalled ribosomes during translation quality control. This process requires ZNF598 ubiquitination and ATP, clearing the way for continued protein synthesis.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • Ribosome collisions occur when translation slows, triggering mRNA and protein quality control pathways.
  • ZNF598 ubiquitin ligase detects persistent ribosome collisions by ubiquitinating the 40S ribosomal subunit.
  • The mechanism for disassembling collided ribosome complexes remains largely undefined.

Purpose of the Study:

  • To elucidate the mechanism of collided ribosome complex disassembly.
  • To define the role of the ASC-1 complex (ASCC) in ribosome-associated quality control.

Main Methods:

  • Reconstitution of collided polysome disassembly in a mammalian cell-free system.
  • Biochemical assays to determine the requirements for disassembly, including ubiquitination and ATP dependence.

Main Results:

  • The conserved ASC-1 complex (ASCC), featuring the ASCC3 helicase, disassembles the leading ribosome in an ATP-dependent manner.
  • Ribosome disassembly by ASCC necessitates 40S ubiquitination by ZNF598 but does not require GTP-dependent factors like Pelo-Hbs1L.
  • Trailing ribosomes can resume translation after the roadblock is removed and are only targeted if they subsequently collide.

Conclusions:

  • ASCC plays a specific role in ribosome-associated quality control by disassembling collided ribosomes.
  • ZNF598-mediated ubiquitination is a prerequisite for ASCC-mediated disassembly.
  • This study identifies ASCC as the molecular factor responsible for removing stalled ribosomes, ensuring translation fidelity.
Keywords:
ASCC3RQChelicasequality controlribosometranslation

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