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Updated: Jun 22, 2026

Measurement of Poly A Tail Length from Drosophila Larva Brain and Cell Line
Published on: January 12, 2024
Poly(A) tail length is controlled by the nuclear poly(A)-binding protein regulating the interaction between poly(A)
Uwe Kühn1, Miriam Gündel, Anne Knoth
1Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 3, 06120 Halle, Germany.
Abstract:
Poly(A) tails of mRNAs are synthesized in the cell nucleus with a defined length, approximately 250 nucleotides in mammalian cells. The same type of length control is seen in an in vitro polyadenylation system reconstituted from three proteins: poly(A) polymerase, cleavage and polyadenylation specificity factor (CPSF), and the nuclear poly(A)-binding protein (PABPN1). CPSF, binding the polyadenylation signal AAUAAA, and PABPN1, binding the growing poly(A) tail, cooperatively stimulate poly(A) polymerase such that a complete poly(A) tail is synthesized in one processive event, which terminates at a length of approximately 250 nucleotides. We report that PABPN1 is required to restrict CPSF binding to the AAUAAA sequence and to permit the stimulation of poly(A) polymerase by AAUAAA-bound CPSF to be maintained throughout the elongation reaction. The stimulation by CPSF is disrupted when the poly(A) tail has reached a length of approximately 250 nucleotides, and this terminates processive elongation. PABPN1 measures the length of the tail and is responsible for disrupting the CPSF-poly(A) polymerase interaction.
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