Paclitaxel activation of the GADD153 promoter through a cellular injury response element containing an essential Sp1 binding site

The GADD153 promoter is transcriptionally activated by paclitaxel-induced injury. Promoter deletion from -786 to -85 base pairs relative to the start of transcription had no significant effect on activation, but deletion to the TATA box abolished it. Placement of the 39 bases from -74 to the TATA box (cellular injury response element, CIRE) upstream of the adenovirus E4 TATA box conferred paclitaxel inducibility. The only consensus sequence present in the CIRE is an Sp1 site; mutation of this site inhibited paclitaxel activation. Paclitaxel failed to activate a SV40-driven luciferase construct containing five Sp1 sequences, and Sp1 sites further upstream in the GADD153 promoter were not essential for activation. Pure Sp1 and nuclear extracts from uninjured and paclitaxel-injured cells protected the same region from -62 to -48 bases on the noncoding strand and -74 to -53 on the coding strand. Nuclear extracts shifted the CIRE to the same extent as purified Sp1 but had no effect on a CIRE with a mutated Sp1 site in gel shift assays. Immunodepletion of Sp1 abolished the shift; antibody to Sp1 produced a supershift. These data indicate that paclitaxel activates the GADD153 promoter through a constitutively occupied Sp1 site at -61 bases.