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Small-Molecule Targeting of RNA Polymerase I Activates a Conserved Transcription Elongation Checkpoint

Ting Wei1, Saman M Najmi2, Hester Liu3

  • 1Division of Pharmaceutical Biosciences, Faculty of Pharmacy and Institute of Biotechnology, University of Helsinki, Helsinki 00014, Finland.

Cell Reports
|April 12, 2018
PubMed

Insights

BMH-21, a cancer therapy drug, triggers the degradation of RNA polymerase I (Pol I) by halting its transcription. This mechanism, involving polymerase pausing, is conserved across species and offers a new therapeutic target.

Area of Science:

  • Molecular Biology
  • Cancer Therapeutics
  • Biochemistry

Background:

  • RNA polymerase I (Pol I) inhibition is a key strategy in cancer therapy.
  • BMH-21 is a novel small molecule that inhibits Pol I transcription and induces enzyme degradation.
  • The precise mechanism underlying BMH-21's action remains unclear.

Purpose of the Study:

  • To elucidate the molecular mechanism by which BMH-21 induces RNA polymerase I degradation.
  • To identify the key factors and cellular processes involved in the BMH-21 response.
  • To determine if the BMH-21 mechanism is conserved and its implications for cancer therapy.

Main Methods:

  • Investigated BMH-21's effects using biochemical assays and genetic analyses in yeast and human cell models.
  • Utilized a reconstituted Pol I transcription system to study direct interactions.
  • Analyzed the role of Pol I subunits and preinitiation factors in BMH-21-induced degradation.

Main Results:

  • BMH-21-mediated degradation of the RPA194 subunit requires Pol I preinitiation factors and other polymerase subunits like RPA135.
  • The inhibitory and degradation effects of BMH-21 on Pol I are conserved in yeast.
  • Transcription elongation defects in Pol I lead to hypersensitivity to BMH-21.
  • BMH-21 directly impairs Pol I transcription elongation, causing prolonged polymerase pausing.

Conclusions:

  • BMH-21 activates a conserved regulatory checkpoint that monitors Pol I transcription.
  • The drug's mechanism involves direct impairment of transcription elongation and polymerase pausing.
  • These findings define a novel therapeutic strategy targeting Pol I in cancer treatment.
Keywords:
cancer therapeuticselongationnucleolusrRNAtranscriptionyeast

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