An A/T-rich motif and an E box mediate the induction of the ART1 proximal promoter activity during myogenesis. Candidate motifs for mediating muscle-specific expression of the mouse proximal ART1 promoter were altered by site-directed mutagenesis of the pART1-S (-322/+37) containing pGL4.10 plasmid. Cells at different stages of differentiation were transfected with the plasmids. Promoter activities were determined using the dual luciferase reporter assays normalized to renilla luciferase activity. Following symbols are used: black box – A/T-rich element (A/T); black oval – E box (E); white box – TATA box (TB) and 'luc' boxed – firefly luciferase gene. An arrow indicates the transcription start site numbered with +1. Mutations of symbolised A/T-rich element (A/T) and E box (E) are indicated by an X overlay. The data represent means ± S.D. of three independent experiments in triplicate.