Figure 1.

Regulation of A28-RGS14 gene expression by p53 and genotoxic stress. (A) Regulation by exogenous p53. The metallothionein-promoter driven p53 transgene in EB1 colon carcinoma cells (9) was induced by the addition of CdCl₂ (6 μM) to the cell culture medium. Total RNA or protein was prepared from cells at the times (in hours) indicated. Northern blots (A) were prepared and analyzed by hybridization with ³²P-labeled cDNA probes corresponding to A28-RGS14, p21^WAF1, p53, or GAPDH. (B) Induction of A28-RGS14 expression by endogenous p53. Northern blot analysis of RKO (colon carcinoma cells, wild-type p53) and clonal RKO-E6 cells (express human papillomavirus E6 viral protein and consequently do not express significant levels of p53) treated with increasing concentrations of doxorubicin for 16 h. (C) Induction of A28-RGS14 transcripts in human cells that are wild type (WT) (MCF-7, breast carcinoma cells; MCF-7 subclone 6; U87, astrocytoma cells) but not mutant (T98G; glioblastoma cells, MCF-7Adr.; doxorubicin-resistant MCF7 subclone) or null (HL-60, promyelocytic leukemia cells) for p53. Cell lines were treated with (lanes D) or without (lanes C) doxorubicin (1 μM) for 16 h. RNA was prepared and analyzed by Northern blot as described in A.