FIG. 2.

MyoD and class I bHLH proteins have the ability to activate the λ5 promoter together with EBF. Panel A shows a diagram of the relative luciferase activity after transfection of 200 ng of λ5 promoter-controlled luciferase reporter plasmid with 300 ng of expression plasmid encoding either Heb, E2-2, or MyoD and 150 ng of either empty (−) or EBF-encoding (+) expression plasmids into HeLa cells. The fold induction was based on the activity obtained when the reporter plasmid was transfected together with 450 ng of empty expression plasmid or 900 ng of empty plasmid when 900 ng of MyoD plasmid was used. The data shown are based on three transfection experiments. Error bars indicate standard deviations. Panel B shows the relative induction of 200 ng of luciferase reporter gene under the control of a basal promoter and two copies of a μE5-μE2 combination from the IgH intron enhancer after transfection of 600 ng of empty, E47-expressing (58), or MyoD-encoding expression plasmid into HeLa cells. The induction was based on data from three representative transfections, and the error bars indicate standard deviations. (C) Relative inductions of 200 ng of reporter constructs controlled either by a basal fos promoter or two copies of the E3-E2 combination (58) from the 5′ part of the λ5 promoter cloned 5′ of the basal fos promoter after transfection with E47 or MyoD expression plasmids in HeLa cells as indicated. The data are collected from three representative transfections, and the error bars indicate the standard deviations.