Analysis of Dβ1 promoter activity in reporter gene constructs in p5424 pro-T cells. (A) Depiction of the D-J-Cβ1 region and the ▵2184 genomic fragment used in the reporter assay, which corresponds to −2184 to +151 relative to the first base of Dβ1. (B) Orientation-specific promoter activity of the ▵2184 fragment in the presence or absence of the Eβ or SV40 (Esv) enhancers. (C) Promoter activity of nested deletions from the 5′ end of the ▵2184 fragment in the presence of the Eβ enhancer. (D) Promoter activity in constructs containing 3′ deletions of the ▵524 genomic fragment, subfragments corresponding to −147 to +6 and −303 to −147, and site-directed mutations of putative Ikaros/Lyf-1 (m35) and GATA (m74) transcription factor sites. Constructs containing genomic fragments in the reverse orientation are indicated by a left-hand arrow. Luciferase activity measured 24 hours after transfection was corrected for transfection efficiency and expressed as a percentage of the pGL-3 control SV40 promoter/enhancer construct. The mean and standard error for four independent transfections are given.