【摘要】： 紫外線是引起DNA損傷常見的物理因素。根據(jù)日光中紫外線波長(zhǎng)的不同，可將其分為3種：UVA(315—400nm)、UVB(280—315nm)和UVC(200—280nm)。其中UVC較前兩者造成的DNA損傷重一些。過量的紫外線照射皮膚可誘發(fā)皮膚癌。 近日節(jié)律廣泛存在于生物體內(nèi)，其周期在24小時(shí)左右，故稱為近日節(jié)律(circadian rhythm)。人體的許多生理、生化參數(shù)均有近日節(jié)律的特點(diǎn)，如睡眠一覺醒、體溫、血壓、心率等，均表現(xiàn)出明顯的近日節(jié)律。 Period2是近日節(jié)律基因家族的重要一員。研究發(fā)現(xiàn)，Period2和腫瘤的發(fā)生發(fā)展有密切的關(guān)系。本實(shí)驗(yàn)室發(fā)現(xiàn)，Period2過表達(dá)能夠減輕γ射線對(duì)細(xì)胞的損傷作用，降低細(xì)胞對(duì)γ射線的敏感性。紫外線也能夠引起細(xì)胞的損傷，其機(jī)制可能與γ射線引起DNA破壞類似。據(jù)此推測(cè)，Period2基因可能在紫外線引起細(xì)胞損傷方面有一定的作用。 本文首先誘導(dǎo)體外培養(yǎng)的細(xì)胞產(chǎn)生近日節(jié)律，在Period2表達(dá)處于峰值和谷值的時(shí)候給與紫外線照射。流式細(xì)胞術(shù)、克隆形成實(shí)驗(yàn)和彗星電泳實(shí)驗(yàn)的結(jié)果發(fā)現(xiàn)，不同組細(xì)胞的凋亡率、細(xì)胞周期分布和細(xì)胞的生長(zhǎng)能力具有顯著性的差異。然后，，將Period2真核表達(dá)質(zhì)粒轉(zhuǎn)染入體外培養(yǎng)細(xì)胞中，增加細(xì)胞的Period2表達(dá)。發(fā)現(xiàn)Period2高表達(dá)的細(xì)胞與對(duì)照組細(xì)胞相比，紫外線引起的凋亡率、細(xì)胞周期分布和細(xì)胞的生長(zhǎng)能力改變具有顯著性的差異。 紫外線照射可引起DNA的單鏈斷裂、雙鏈斷裂及環(huán)丁烷嘧啶二聚體形成，這種損傷可經(jīng)DNA修復(fù)系統(tǒng)進(jìn)行修復(fù)。通過彗星實(shí)驗(yàn)，提示Period2基因過表達(dá)有抑制紫外線DNA損傷并促進(jìn)DNA修復(fù)的作用。
[Abstract]:Ultraviolet radiation (UV) is a common physical factor causing DNA damage. According to the wavelength of ultraviolet light, it can be divided into three kinds of: UVA (315-400nm), UVB (280-315nm and UVC (200-280nm). The DNA damage caused by UVC was more serious than that caused by the former two. Excessive ultraviolet radiation can induce skin cancer. Circadian rhythm exists widely in organisms and its cycle is about 24 hours, so it is called circadian (circadian rhythm). Many physiological and biochemical parameters of the human body are characterized by circadian rhythm, such as sleep arousal, body temperature, blood pressure, heart rate and so on. Period2 is an important member of the circadian gene family. The study found that Period2 has a close relationship with tumorigenesis and development. Our laboratory found that overexpression of Period2 can attenuate the damage of 緯-ray and decrease the sensitivity of cells to 緯-ray. UV can also cause cell damage, which may be similar to 緯-ray-induced DNA damage. It is suggested that Period2 gene may play a role in ultraviolet-induced cell damage. In this study, cells were induced to produce circadian rhythms and were exposed to ultraviolet light at peak and valley levels of Period2 expression. The results of flow cytometry clone formation assay and comet electrophoresis showed that there were significant differences in apoptosis rate cell cycle distribution and cell growth ability between different groups. Then, the eukaryotic expression plasmid of Period2 was transfected into cultured cells in vitro to increase the expression of Period2. It was found that there were significant differences in the apoptosis rate, cell cycle distribution and cell growth ability between the cells with high expression of Period2 and those of the control group. Ultraviolet irradiation can cause single strand break, double strand break and formation of cyclobutane pyrimidine dimer in DNA. This damage can be repaired by DNA repair system. Comet assay suggested that overexpression of Period2 gene could inhibit the damage of ultraviolet DNA and promote the repair of DNA.
【學(xué)位授予單位】：四川大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2007
【分類號(hào)】：R363

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