Barx2 and the HBS potentiate activation of the SMA promoter by MyoD.
A, sequence of the 300-bp proximal SMA promoter region used in SMA
promoter-luciferase reporter constructs. B, luciferase assay of the
SMA promoter construct transfected into primary limb bud cells from
Barx2+/– and Barx2–/– mice shows that
Barx2 is required for full promoter activity. C, co-transfection of
the SMA promoter construct with Barx2:pcDNA3, MyoD:pcDNA3, or both MyoD:pcDNA3
and Barx2:pcDNA3 plasmids in C2C12 cells shows that Barx2 cooperates with MyoD
to increase SMA promoter activity. Co-transfection of the ΔHBS-SMA
promoter construct with the same effector plasmids shows that mutation of the
HBS element prevents cooperative activation by Barx2 and MyoD. Promoter
activity is in arbitrary units, and experiments were performed at least four
times. All values are significant at p < 0.05.