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Updated: Aug 15, 2026

Exploring Sequence Space to Identify Binding Sites for Regulatory RNA-Binding Proteins
Published on: August 9, 2019
PTB regulates the processing of a 3'-terminal exon by repressing both splicing and polyadenylation
Caroline Le Sommer1, Michelle Lesimple, Agnès Mereau
1UMR 6061 CNRS-Université de Rennes 1, IFR 140 Faculté de Médecine, CS 34317, 35043 Rennes Cedex, France.
Abstract:
The polypyrimidine tract binding protein (PTB) has been described as a global repressor of regulated exons. To investigate PTB functions in a physiological context, we used a combination of morpholino-mediated knockdown and transgenic overexpression strategies in Xenopus laevis embryos. We show that embryonic endoderm and skin deficient in PTB displayed a switch of the alpha-tropomyosin pre-mRNA 3' end processing to the somite-specific pattern that results from the utilization of an upstream 3'-terminal exon designed exon 9A9'. Conversely, somitic targeted overexpression of PTB resulted in the repression of the somite-specific exon 9A9' and a switch towards the nonmuscle pattern. These results validate PTB as a key physiological regulator of the 3' end processing of the alpha-tropomyosin pre-mRNA. Moreover, using a minigene strategy in the Xenopus oocyte, we show that in addition to repressing the splicing of exon 9A9', PTB regulates the cleavage/polyadenylation of this 3'-terminal exon.
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