The Regulatory Mechanism Study Of ASPP1 By EGR-1

ASPP1 is a tumor suppressor of the ASPPs family, which was a newly discovered protein family. Lots of studies found that ASPP1 was decreased in many types of tumor tissue. It is very important to find the reasons of this downregulation. The upstream regulatory mechanisms of this gene is the key to explain these phenomena. Some epigenetic regulatory mechanisms of ASPP1 have been found, but the transcript factors which can bind with ASPP1 promoter were found only in E2 F family.In this study, we mainly studied the regulatory mechanism of ASPP1 by EGR-1 and their biological functions under the quercetin treatment. When we overexpressed exogenous EGR-1 and knockdown endogenous EGR-1, the transcriptional level and protein expression level of ASPP1 was related to the expression of EGR-1. After these relationship of these two genes have been found, we want to know whether EGR-1 can be a transcriptional factor which can regulate the transcription level of ASPP1. Firstly, we did luciferase assay, the experiments results showed EGR-1 can regulate the promoter activity of ASPP1 positively. This promoter was(-1040—+88) region of ASPP1, and then we found that the core region of EGR-1 binding was(-284—+88). The Ch IP assay results indicated that EGR-1 can really bind with the(-284—+88) promoter region of ASPP1, and these results were the same with the luciferase assay. All these experiments make sure that EGR-1 can really regulate the expression of ASPP1 as a transcription factor.Quercetin is known as a plant extract, has been reported by many researches that it has the apoptotic function in different cancer cell lines, but the mechanisms of this phenomenon have not been clarified. Our recent studies showed that, under the treatment of quercetin, the expression level of ASPP1 and EGR-1 were both increased. These discoveries indicated that, tumor suppressor ASPP1 may take part in the apoptotic function treated with quercetin induced by EGR-1. Through the Ch IP assay, we found the bind abilities of EGR-1 with the promoter of ASPP1 was increased. This results implied that EGR-1 activated the expression of ASPP1 under this treatment. After knocking down EGR-1 and ASPP1, we treated these cells with quercetin. Analysed the number of the apotosis cells by FACS, we found the inhibition of apoptosis was the main reason that the cell ability was increased.In conclusion, in this study we found EGR-1 can regulate the expression of ASPP1 by binding with its promoter. This new find made a contribution to explain why ASPP1 was downregulated in many tumor tissues. At the same time, this study also set up a new direction and pathway for the mechanism of the apoptosis caused by quercetin. These new discoveries made it better for us to understand the mechanisms of tumor development and progression, and can make contributions to find new targets and theoretical basis of tumor prevention and therapy.