Processing of the ribosomal ubiquitin-like fusion protein FUBI-eS30/FAU is required for 40S maturation and depends on USP36

Elife. 2021 Jul 28:10:e70560. doi: 10.7554/eLife.70560.

Abstract

In humans and other holozoan organisms, the ribosomal protein eS30 is synthesized as a fusion protein with the ubiquitin-like protein FUBI. However, FUBI is not part of the mature 40S ribosomal subunit and cleaved off by an as-of-yet unidentified protease. How FUBI-eS30 processing is coordinated with 40S subunit maturation is unknown. To study the mechanism and importance of FUBI-eS30 processing, we expressed non-cleavable mutants in human cells, which affected late steps of cytoplasmic 40S maturation, including the maturation of 18S rRNA and recycling of late-acting ribosome biogenesis factors. Differential affinity purification of wild-type and non-cleavable FUBI-eS30 mutants identified the deubiquitinase USP36 as a candidate FUBI-eS30 processing enzyme. Depletion of USP36 by RNAi or CRISPRi indeed impaired FUBI-eS30 processing and moreover, purified USP36 cut FUBI-eS30 in vitro. Together, these data demonstrate the functional importance of FUBI-eS30 cleavage and identify USP36 as a novel protease involved in this process.

Keywords: DUB; FUBI; biochemistry; cell biology; chemical biology; human; nucleolus; ribosome biogenesis; translation; ubiquitin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cloning, Molecular
  • Gene Deletion
  • Gene Expression Regulation / physiology*
  • HeLa Cells
  • Humans
  • RNA Processing, Post-Transcriptional
  • Ribosomal Proteins / genetics
  • Ribosomal Proteins / metabolism*
  • Ribosome Subunits, Small, Eukaryotic*
  • Ubiquitin Thiolesterase / genetics
  • Ubiquitin Thiolesterase / metabolism*
  • Ubiquitins / genetics
  • Ubiquitins / metabolism*

Substances

  • Ribosomal Proteins
  • USP36 protein, human
  • Ubiquitins
  • FAU protein, human
  • Ubiquitin Thiolesterase

Grants and funding

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.