PTB regulates the processing of a 3'-terminal exon by repressing both splicing and polyadenylation.
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.
Le Sommer
Caroline
C
UMR 6061 CNRS-Université de Rennes 1, IFR 140 Faculté de Médecine, CS 34317, 35043 Rennes Cedex, France.
Lesimple
Michelle
M
Mereau
Agnès
A
Menoret
Severine
S
Allo
Marie-Rose
MR
Hardy
Serge
S
D000185:Actinin / Q000235:genetics; D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning; D002454:Cell Differentiation; D004625:Embryo, Nonmammalian; D004707:Endoderm / Q000378:metabolism; D005091:Exons; D026723:Polyadenylation; D038941:Polypyrimidine Tract-Binding Protein / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics; D026721:RNA 3' End Processing; D012322:RNA Precursors / Q000378:metabolism; D012326:RNA Splicing; D012867:Skin / Q000378:metabolism; D019170:Somites / Q000166:cytology / Q000378:metabolism; D014335:Tropomyosin / Q000235:genetics*; D014982:Xenopus laevis
D020033:Protein Isoforms; D012322:RNA Precursors; D014335:Tropomyosin; D000185:Actinin; D038941:Polypyrimidine Tract-Binding Protein