Previously we described the isolation of a stress response gene, gaddl53, whose expression was induced following treatment of cells with agents that either damage DNA or arrest cellular growth. DNA damage generally leads to a delay in cell cycle progression. Thus, it is possible that the expression of gaddl53 following DNA damage is important in controlling the proliferation of damaged cells, or in otherwise protecting them from potentially lethal or permanent effects of the damage. Our studies over the past year have contributed significantly to the understanding of the transcriptional regulation of gaddl53. The importance of various regions in the 5'portion of this gene in regulating its response to DNA damage and the inhibition of DNA synthesis has been evaluated. Using deletion analysis we have identified two regions within the promoter which are necessary for the increased transcription of the gaddl53 gene following DNA damage. The major DNA damage responsive element lies within the region from -305 to -224 and encompasses an AP-1 transcriptional factor binding site. We have provided evidence for the presence of specific cellular factors which bind to this AP-1 site and have shown that the level of binding activity is increased following DNA damage. A second DNA damage responsive element lies within the region from -141 to -36. The promoter fragments thus far examined are not responsive to treatments which induce growth arrest suggesting that the gene is differentially regulated by DNA damage and growth arrest not associated with genotoxic agents.
