Transcriptional activity of the 4 predicted promoters within the mylk1 gene. Luciferase reporter genes were generated containing genomic fragments (700 and 750 bp, respectively) immediately 5′ of exons E1 (220 E1) or E1* (220E1*) or comprising nucleotides −389 to +115 of the 130-kDa MLCK (130) promoter, −190 to +180 of the telokin (Tel) promoter, or −113 to +20 of the thymidine kinase (TK) promoter. These reporter plasmids or the empty luciferase vector pGL2B were transfected into 10T1/2 embryonic fibroblasts of A10 smooth muscle cells, together with an internal control renilla luciferase plasmid. At 24 h after transfection, lysates were prepared and analyzed for luciferase activity. Results presented are relative light units (RLU) of luciferase activity normalized to the renilla luciferase internal control. Values are means ± SE of 6 samples.