Transcription factors Sp1 and Sp3 increase P2-promoter activity in DRG neurons. P2- promoter reporter plasmid (0.4 kb) directs an ~8 fold increase in luciferase activity when compared with the empty reporter control (pGL-E). When construct 0.4 kb is co-transfected with a plasmid expressing Sp1, or Sp3, a significant increase in promoter activity was observed. However, co-transfection of Sp4 or a combination of Sp1/Sp3, Sp1/Sp4 or Sp3/Sp4 (equal ratios) failed to increase promoter activity beyond what was observed with the 0.4 kb alone. Error bars SEM (n = 3) triplicate measures. Significant differences: ANOVA (**) p < 0.01, (*) p < 0.05.