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Updated: Aug 14, 2026

Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro
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Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro

Published on: May 3, 2014

Poly(A) polymerase purified from HeLa cell nuclear extract is required for both cleavage and polyadenylation of

G Christofori1, W Keller

  • 1Department of Cell Biology, University of Basel, Switzerland.

Molecular and Cellular Biology
|January 1, 1989
PubMed

Insights

Poly(A) polymerase (PAP) from HeLa cells plays a dual role in mRNA processing. This enzyme is crucial for both the specific cleavage and polyadenylation of pre-mRNA 3'-ends.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • RNA Processing

Background:

  • Messenger RNA (mRNA) 3 -end formation is a critical step in gene expression.
  • Polyadenylation, the addition of a poly(A) tail, influences mRNA stability and translation.
  • The enzyme poly(A) polymerase (PAP) is central to this process, but its precise role in specific pre-mRNA processing is complex.

Purpose of the Study:

  • To investigate the role of poly(A) polymerase (PAP) in the 3 -end processing of polyadenylated mRNA.
  • To characterize the enzymatic activities and cofactor requirements of partially purified PAP from HeLa cell nuclear extract.

Main Methods:

  • Partial purification of poly(A) polymerase (PAP) from HeLa cell nuclear extract.
  • In vitro assays to assess PAP activity with different divalent metal ions (Mn2+ and Mg2+).
  • Testing the requirement for accessory factors (cleavage and polyadenylation factor, cleavage factor) in specific RNA processing.

Main Results:

  • Partially purified PAP (50-60 kDa) nonspecifically polyadenylated RNA in the presence of Mn2+.
  • With Mg2+, PAP required a cleavage and polyadenylation factor for specific polyadenylation of pre-cleaved substrates with an intact AAUAAA sequence.
  • The same PAP fraction was essential for specific pre-mRNA cleavage, indicating a dual function.

Conclusions:

  • The purified PAP fraction possesses both poly(A) polymerase and cleavage activities.
  • These two activities could not be separated during extensive purification, suggesting they reside in a single PAP component.
  • This single PAP component is essential for the specific cleavage preceding pre-mRNA polyadenylation.

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