CELF and PTB proteins modulate the inclusion of the beta-tropomyosin exon 6B during myogenic differentiation

Exon 6B from the chicken beta-tropomyosin pre-mRNA is alternatively spliced during myogenic differentiation Exon 6B is excluded in mRNA from myoblasts and Included in mRNA from myotubes We investigated the regulation of exon 6B inclusion ex vivo in a quail myogenic cell line which behaves as myoblasts in undifferentiated state and as myotubes after differentiation We show that the beta-tropomyosin exon 6B is a novel target of CUG-BP and ETR-3-like factor (CELF) Overexpression of CELF proteins in myoblasts activates splicing of exon 6B Using a dominant-negative form of CELF4 we demonstrate that CELF proteins are involved in switching splicing from exon 6A towards exon 6B inclusion during myogenic differentiation We also found that polypyrimidine tract binding protein (PTB) is required for splicing repression of exon 6B in myoblasts CELF and PTB proteins exhibit antagonistic properties toward inclusion of exon 6B during myogenic differentiation Our results suggest that a change in the protein level of CUGBP1 and PTB proteins associated with a distinct pattern of PTB during the transition from myoblasts to myotubes is one of the parameters involved in regulating splicing of exon 68 during myogenesis (C) 2010 Elsevier Inc All rights reserved