Effect of 5′ deletion of the PAI-1 gene on basal and D dimer-inducible PAI-1 transcriptional activity. Progressive deletions of the 5′ flanking region of the PAI-1 gene were generated by restriction digestion or PCR and ligated to a luciferase-encoding reporter plasmid. The plasmids were transiently transfected into rat lung fibroblasts along with the thymidine kinase promoter-Renilla luciferase encoding plasmid. For determination of promoter activity, cells were incubated for 48 hours posttransfection in 0.4% serum containing media followed by either serum-free media ([A], right, basal activity) or SFM plus D dimer (1.1 μmol/L; [B], inducible activity) for 6 hours. Raw data are tabulated as the ratio of firefly luciferase activity to that of its Renillaluciferase activity (mean ± SD) and reported relative to the value for the p928 plasmid (assigned value of 100). *P < .05 relative to the p928 values. +P < .05 relative to the p161wt values by ANOVA/Newman-Keuls test. (A) Relative basal activity. Constructs are as indicated at left. Mutations were performed at the AP-1–like site (−59 to −52) of the PAI-1 gene with otherwise intact −161 to +26. PAIcon marks the TGAGTCA element, PAIwt marks the TGAGTTCA element, and PAImut marks the TGTGTTTG element at the −59 to −52 positions of p161. Underscored letters denote deviations from the consensus AP-1 element. (B) D dimer-inducible transcriptional activity. Transfected plasmids are as indicated.