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Tor1 and CK2 kinases control a switch between alternative ribosome biogenesis pathways in a growth-dependent manner

Isabelle C Kos-Braun1, Ilona Jung1, Martin Koš1

  • 1Biochemistry Center, University of Heidelberg, Heidelberg, Germany.

Plos Biology
|March 11, 2017
PubMed

Insights

The Target of rapamycin 1 (Tor1) pathway controls ribosome production during stress. This study reveals Tor1 and casein kinase 2 (CK2) regulate pre-ribosomal RNA processing post-transcriptionally, halting new ribosome synthesis.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Ribosome biogenesis is a critical, energy-intensive cellular process.
  • The Target of rapamycin 1 (Tor1) pathway is known to regulate ribosomal RNA (rRNA) synthesis transcriptionally.
  • The posttranscriptional regulation of ribosome biogenesis remains largely uncharacterized.

Purpose of the Study:

  • To investigate the posttranscriptional control mechanisms of ribosome biogenesis.
  • To determine the role of Tor1 and casein kinase 2 (CK2) in regulating pre-ribosomal RNA (pre-rRNA) processing.
  • To identify novel signaling pathways involved in ribosome biogenesis regulation under stress conditions.

Main Methods:

  • Utilized yeast as a model organism.
  • Investigated the effects of Tor1 and CK2 kinases on pre-rRNA processing pathways.
  • Analyzed the role of Sch9 kinase in the stress-induced regulation of ribosome biogenesis.

Main Results:

  • Demonstrated that Tor1 and CK2 kinases control a rapid switch in pre-rRNA processing pathways in yeast.
  • Showed that under stress, pre-rRNA synthesis continues but is processed into non-productive forms, halting ribosome production.
  • Found that this regulatory switch is independent of Sch9 kinase activity.

Conclusions:

  • Identified a novel TOR Complex 1 (TORC1) signaling pathway involving CK2 that directly regulates ribosome biogenesis at the posttranscriptional level.
  • Established that Tor1 and CK2 kinases mediate a rapid response to cellular stress by altering pre-rRNA processing.
  • Highlighted a previously unrecognized mechanism for controlling ribosome production independent of transcriptional regulation and Sch9 kinase.

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