Figure 3.

Repression of serum-induced ATF3 reporter activity in c-myc-deficient cells. (A) Human and rat ATF3 gene promoters with putative consensus elements for ATF/CREB, AP1, c-Myc/USF, and other factors are aligned (Liang et al, 1996). Human ATF3 reporter plasmids containing various deletions or two point mutations of ATF/CRE site are also depicted. (B) Serum induction of ATF3 promoter activity was assayed in wild-type TGR1 cells using pATF3Luc1850 in the presence or absence of 25 μM PD98059 for 24 h. Results are mean±s.d. of triplicate assays. Significant induction by serum compared with control, ^*P<0.05. (C) Wild-type cells were transfected with ATF3 reporters containing various deletions or ATF/CRE point mutations, and assayed for serum induction. Relative activity to that of minimal promoter pATF3Luc-84 was the mean with s.d. of triplicate experiments. Significant induction by serum compared with control, ^*P<0.05. (D) c-myc-deficient cells were transfected with various reporter plasmids along with empty, LacZ or c-Myc expression vectors and treated with 10% serum. Fold induction by serum is shown and represents the mean with s.d. of triplicate experiments. Significant induction by c-Myc compared with control, ^*P<0.05.