Proteasome-mediated processing of Def1, a critical step in the cellular response to transcription stress

Cell. 2013 Aug 29;154(5):983-995. doi: 10.1016/j.cell.2013.07.028.


DNA damage triggers polyubiquitylation and degradation of the largest subunit of RNA polymerase II (RNAPII), a "mechanism of last resort" employed during transcription stress. In yeast, this process is dependent on Def1 through a previously unresolved mechanism. Here, we report that Def1 becomes activated through ubiquitylation- and proteasome-dependent processing. Def1 processing results in the removal of a domain promoting cytoplasmic localization, resulting in nuclear accumulation of the clipped protein. Nuclear Def1 then binds RNAPII, utilizing a ubiquitin-binding domain to recruit the Elongin-Cullin E3 ligase complex via a ubiquitin-homology domain in the Ela1 protein. This facilitates polyubiquitylation of Rpb1, triggering its proteasome-mediated degradation. Together, these results outline the multistep mechanism of Rpb1 polyubiquitylation triggered by transcription stress and uncover the key role played by Def1 as a facilitator of Elongin-Cullin ubiquitin ligase function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Chromosomal Proteins, Non-Histone / chemistry
  • Chromosomal Proteins, Non-Histone / metabolism*
  • Molecular Sequence Data
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Structure, Tertiary
  • RNA Polymerase II / metabolism
  • Saccharomyces cerevisiae / physiology*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Sequence Alignment
  • Stress, Physiological
  • Transcription, Genetic*
  • Ubiquitin-Protein Ligase Complexes / metabolism


  • Chromosomal Proteins, Non-Histone
  • DEF1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Ubiquitin-Protein Ligase Complexes
  • RNA Polymerase II
  • Proteasome Endopeptidase Complex