生长激素和糖皮质激素在乙肝病毒影响MAT1A性别差异表达中的作用机制

Hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) occurs more often in men than in women,which is attributed to cytokine-driven liver-gender disruption and not androgen signaling as a mechanism of male-predominant.S-adenosylmethionine (AdoMet, also abbreviated SAM) should not be viewed only as the principal biological methyl donor and a regulator of methionine metabolism, but also as an intracellular signal that controls essential hepatic functions such as hepatocyte growth and differentiation as well as sensitivity to liver injury. AdoMet is synthesized from L-methionine and ATP in a two-step reaction , which is catalyzed by the enzyme methionine adenosyltransferase (MAT, abbreviated SAM synthetase). We found that MAT1A is a important Sexually Dimorphic Liver Gene.Promoter analysis showed that Growth hormone 、Glucocorticoid 、sex hormone make an effect on MAT1A promoter activity and expression and there are multiple nuclear hormone receptor binding sites in the MAT1A promoter sequence. Hepatitis B virus (HBV) core promoter also contains multiple binding sites for nuclear receptors.We guess that HBV can damage liver growth hormone receptor and glucocorticoid receptor signal pathway through competitive binding to nuclear hormone receptors, reduce the expression of MAT1A gene and produce a decrease in the steady-state SAM concentration, which can promote hepatocarcinogensis.We will identify the function of Multiple nuclear hormone receptor response element in the promoter region of MAT1A in this study. And also we will compare the influence of a variety of hormones on MAT1A expression and steady-state SAM concentration in the liver tissue of normal mice and HBV transgenic mouse . We want to understand gender differences mechanisms of HBV-induced liver cancer through hormone regulation. It will provide a strong theoretical basis for liver cancer hormone therapy.?

乙肝病毒(HBV)相关性肝癌的性别差异与肝性别基因表达失调有关。绝大多数肝性别基因的调控及其在HBV致癌机制中的作用不为人所知。生物甲基供体S-腺苷蛋氨酸（SAM）是肝细胞生长、分化的调节信号，其水平降低将导致肝癌的发生。我们前期证实SAM合成的关键酶MAT1A是一种重要的肝性别基因。生长激素（GH）、糖皮质激素（GCs）、性激素均影响MAT1A启动子活性，且该启动子中存在多种激素受体结合位点。我们推测基因组中也存在激素受体结合位点的HBV可能通过竞争性与激素受体的结合损害男性肝脏生长激素和糖皮质激素受体信号通路，抑制MAT1A表达，降低稳态SAM浓度，诱发肝癌的发生。本课题将通过对MAT1A启动子区多个核激素受体位点反应元件的功能鉴定，比较多种激素对正常鼠及HBV转基因鼠肝组织MAT1A表达、表观遗传修饰及SAM浓度的影响来证实我们的推测。并从激素调节水平理解HBV致癌的性别差异机制。

乙肝病毒(HBV)相关性肝癌的性别差异与肝性别基因表达失调有关。绝大多数肝性别基因的调控及其在HBV致癌机制中的作用不为人所知。生物甲基供体S-腺苷蛋氨酸（SAM）是肝细胞生长、分化的调节信号，其水平降低将导致肝癌的发生。本研究证实SAM合成的关键酶MAT1A是一种重要的肝性别基因。我们发现MAT1A及其影响的肝细胞内稳态SAM浓度的性别二型性与雌激素的作用有关。我们发现MAT1A启动子-1855bp~-1874bp为雌激素受体有效的作用元件，雌激素通过雌激素受体结合此作用元件进而促进MAT1A启动子的活性，增加MAT1A的表达。雌激素还可以通过增强miR-26p-5b启动子的活性，进而刺激MAT2A表达，从而影响细胞稳态SAM浓度。进一步，我们发现在药理浓度水平下，糖皮质激素（GCs）通过诱导MAT1A表达，进而诱导SAM的合成。HBV通过上调DNA甲基化转移酶-1（ DNMT1），进而抑制MAT1A的表达。但HBV促进MAT1A启动子甲基化水平，抑制了可被GCs诱导的MAT1A表达。HBV抑制MAT1A表达的机制是通过对MAT1A启动子中GRE位点特异性高甲基化而发挥作用的。IFN-α可通过抗病毒作用抑制HBV表达，进而促进MAT1A表达。GCs诱导的AdoMet合成可重塑STAT1甲基化，并非磷酸化，从而促进STAT1活化。蛋白质精氨酸甲基化转移酶-1（PRMT1）参与AdoMet重塑STAT1甲基化的过程。我们还发现GCs、SAM和IFN-α的联合应用，形成正向反馈环，增加了细胞稳态SAM浓度，从而增强抗HBV活性。.另外，我们针对肝癌组织及癌旁组织小RNA测序时发现一个piRNA：piR25783在癌和癌旁组织中差异明显。我们发现piR25783就是一个来源于tRNA-GLY-GCC的piRNA。piR25783和piwil4有结合，并且其3’末端存在2甲氧基修饰。piR25783在HBV相关性肝癌中低表达，其表达水平和肝癌预后呈正相关。体内外实验证明piR25783抑制肝癌生长，促进细胞凋亡，其分子机制与piR25783通过竞争性结合IMP1从而下调HIF1A/ITGA2/PRKDC的表达有关。