[Effect of 14-3-3sigma on transcriptional activity of p73 gene]

p53 gene is the main regulator of 14-3-3sigma. Activated p53 could induce the expression of 14-3-3sigma, while 14-3-3sigma stabilizes the expression of p53 and enhances its transcriptional activity. p63 and p73, the members of p53 family, also have some functions similar to p53. This study was to investigate the effect of 14-3-3sigma on the transcriptional activity of p73.

Luciferase reporter assay, reverse transcription-polymerase chain reaction (RT-PCR), and Western blot were used to evaluate the effect of 14-3-3sigma on the transcriptional activity of p73 in p53-deficient human lung carcinoma cell line H1299. Colony formation test was used to evaluate the effect of 14-3-3sigma on the transcriptional activity of p73 in p53-mutant human breast cancer cell line MDA-MB-436.

The luciferase activities induced by bax and p21WAF1 promotors were significantly higher in p73-transfected H1299 cells than in control H1299 cells (P<0.01), and were further increased by the transfection of p73 (25 ng) and 14-3-3sigma (100, 200, and 400 ng) in a dose-dependent manner (P<0.01). The expression of bax and p21WAF1 were higher in p73-transfected H1299 cells than in control H1299 cells, and were significantly higher in p73-and 14-3-3sigma-transfected H1299 cells than in p73-transfected H1299 cells (P<0.01). The number of colonies was fewer in p73-transfected MDA-MB-436 cells than in control MDA-MB-436 cells, and the colonies were significantly smaller in p73-and 14-3-3sigma-transfected H1299 cells than in p73-transfected H1299 cells (P<0.01).

14-3-3sigma can enhance the transcriptional activity of p73 in a dose-dependent manner.