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Microprocessor Recruitment to Elongating RNA Polymerase II Is Required for Differential Expression of MicroRNAs

Victoria A Church1, Sigal Pressman1, Mamiko Isaji1

  • 1Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA.

Cell Reports
|September 28, 2017
PubMed

Insights

The Microprocessor complex, containing Drosha and DGCR8, processes microRNAs (miRNAs). Cdk9-phosphorylated RNA polymerase II recruits Microprocessor for co-transcriptional processing of specific pri-miRNAs, impacting cellular miRNA levels.

Area of Science:

  • Molecular Biology
  • Gene Regulation
  • Biochemistry

Background:

  • Cellular microRNA (miRNA) abundance depends on efficient nuclear processing of primary miRNA transcripts (pri-miRNAs) into pre-miRNA intermediates.
  • The Microprocessor complex, comprising Drosha and DGCR8, executes this processing, but factors governing its differential activity remain unclear.

Purpose of the Study:

  • To investigate the regulatory mechanisms controlling the differential processing of pri-miRNAs by the Microprocessor complex.
  • To elucidate the role of RNA polymerase II phosphorylation in pri-miRNA processing.

Main Methods:

  • Investigated the interaction between Drosophila DGCR8 (Pasha) and phosphorylated RNA polymerase II.
  • Utilized Cdk9 kinase inhibition to assess the impact on pri-miRNA processing.
  • Analyzed pri-miRNA processing efficiency based on the presence or absence of a UGU sequence motif.

Main Results:

  • Drosophila DGCR8 (Pasha) directly associates with the phosphorylated C-terminal domain of RNA polymerase II via Cdk9 kinase (pTEFb).
  • Disruption of this association leads to global changes in pri-miRNA processing.
  • Processing of pri-miRNAs with a UGU motif increases, while processing of pri-miRNAs lacking this motif decreases upon Cdk9 inhibition.

Conclusions:

  • Phosphorylation of RNA polymerase II recruits the Microprocessor complex for co-transcriptional processing of non-UGU pri-miRNAs.
  • This mechanism ensures efficient processing of pri-miRNAs that would otherwise be poorly processed.
  • UGU-positive pri-miRNAs are processed independently of RNA polymerase II association.
Keywords:
DGCR8DrosophilaRNA polymerase IImicroRNA

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