FIGURE 1.

MBNL3 promotes exclusion of β-exon from Mef2A and Mef2D transcript during muscle differentiation. A, a schematic diagram of Mef2 alternative splicing and the relative positions of primers used for RT-PCR are provided. The MADS box and the Mef2 domain comprise the highly conserved DNA-binding and dimerization domains. The remainder of the protein represents the transactivation domain. The alternatively spliced β-exon and two forms of the α-exon are shown. B, total RNA was isolated from control (C2C12-control) and MBNL3 (C2C12-MBNL3) expressing C2C12 cells maintained for 0 or 2 days in differentiation media (DM). Splicing pattern of Mef2A and Mef2D was examined by RT-PCR using primers that can distinguish between the (+)β and (−)β isoforms, as diagrammed in A. The levels of Timm17b were measured to control for variations in input RNA. The data shown are representative of four independent experiments.