Figure 3.

Negative elongation factors are required for Hox gene promoter insulator activity. The stalled promoter insulator lines were tested in elongation factor mutant backgrounds. (A–H) The Abd-B/lacZ line was tested in Nelf-E/+ (A,B), Nelf-A/+ (C,D), Spt4/+ (E,F), and Spt5/+ (G,H) backgrounds, and there was loss of insulator activity of the Abd-B promoter in these mutant backgrounds as seen by the appearance of the IAB5 pattern in situ signal when white probe was used (B,D,F,H). (I–P) Similar disruption of the insulator activity was observed for the Ubx/lacZ transgene in different mutant backgrounds of Nelf-E/+ (I,J), Nelf-A/+ (K,L), Spt4/+ (M,N), and Spt5/+ (O,P). (J,L,N,P) The white probe displayed the IAB5 pattern staining in these elongation mutant backgrounds.