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<p>Protein degradation orders events in the cell division cycle in eukaryotes, bacteria, and archaea. In eukaryotes, chromosome segregation and mitotic exit are triggered by proteasome-dependent degradation of securin and cyclin B, respectively. Recent findings show that the archaeal proteasome also targets substrates, including CdvB, for degradation in a cell-cycle-dependent manner in <i>Sulfolobus acidocaldarius</i>—an experimentally tractable archaeal relative of eukaryotes. Here, using CdvB as a model substrate to explore the mechanism of cyclic protein degradation, we demonstrate that the C-terminal broken-winged helix of CdvB, previously shown to bind CdvA, is sufficient to render a fusion protein unstable as cells progress through division. We show that the rate of CdvB degradation accelerates during division in part due to a cell-cycle-dependent increase in expression of the proteasome-activating nucleotidase (PAN), under the control of a cyclically expressed novel transcription factor “CCTF1” that represses PAN expression. Taken together, these findings reveal mechanisms by which archaea, despite lacking cyclin-dependent kinases, control proteasome-mediated degradation to order events during cell division.</p>

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The mechanism of cell-cycle-dependent proteasomal degradation of archaeal ESCRT-III homolog CdvB in Sulfolobus

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月9日

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  • Yin-Wei Kuo,
  • Jovan Traparić,
  • Sherman Foo,
  • Buzz Baum

摘要

Protein degradation orders events in the cell division cycle in eukaryotes, bacteria, and archaea. In eukaryotes, chromosome segregation and mitotic exit are triggered by proteasome-dependent degradation of securin and cyclin B, respectively. Recent findings show that the archaeal proteasome also targets substrates, including CdvB, for degradation in a cell-cycle-dependent manner in Sulfolobus acidocaldarius—an experimentally tractable archaeal relative of eukaryotes. Here, using CdvB as a model substrate to explore the mechanism of cyclic protein degradation, we demonstrate that the C-terminal broken-winged helix of CdvB, previously shown to bind CdvA, is sufficient to render a fusion protein unstable as cells progress through division. We show that the rate of CdvB degradation accelerates during division in part due to a cell-cycle-dependent increase in expression of the proteasome-activating nucleotidase (PAN), under the control of a cyclically expressed novel transcription factor “CCTF1” that represses PAN expression. Taken together, these findings reveal mechanisms by which archaea, despite lacking cyclin-dependent kinases, control proteasome-mediated degradation to order events during cell division.