Transcription factors Oct-1 and NF-YA regulate the p53-independent induction of the GADD45 following DNA damage

The p53-regulated GADD45 gene is one of the important players in cellular r esponse to DNA damage, and probably involved in the control of cell cycle c heckpoint, apoptosis and DNA repair, There are both the p53-dependent and - independent pathways that regulate GADD45 induction. Following ionizing rad iation, induction of the GADD45 gene is regulated by p53 through the p53-bi nding motif located in the third intron of the GADD45 gene. In contrast, GA DD45 induction by methyl methanesulfonate (MMS), UV radiation (UV), and med ium starvation is independent of p53 status although p53 may contribute to these responses. However, the regulatory elements that control the p53-inde pendent induction of GADD45 remain uncertain. In this report, we have perfo rmed detailed analyses to characterize the responsive components that are r equired for the induction of the GADD45 promoter. We have found that the re gion between -107 and -62 of the GADD45 promoter is crucial for the inducti on. Sequence analysis indicates that there are two OCT-1 sites and one CAAT box located in this region. Site-directed mutations of both OCT-1 and CAAT motifs substantially abrogate the induction of the GADD45 promoter by DNA damage. In addition, both Oct-1 protein (binding to OCT-1 site) and NP-YA p rotein (binding to CAAT hox) are induced after cell exposure to DNA damagin g agents. Moreover, the Electrophoretic Mobility Shift Assay (EMSA) has dem onstrated the direct bindings of Oct-1 and NF-YA proteins to their consensu s sequences in the GADD45 promoter. Therefore, these results have presented the novel observation that transcription factors Oct-1 and NF-YA participa te in the cellular response to DNA damage and are involved in the regulatio n of stress-inducible genes.