Mitochondrial rRNA Methylation: Effects of ethanol/SAMe

描述（由申请人提供）： 建议研究以下假设：慢性乙醇喂养导致肝脏S-腺苷-L-甲硫氨酸（Adomet）水平降低，这种缺乏导致线粒体核糖体组装受损和蛋白质合成抑制。已发表的数据表明，乙醇对肝脏中的氧化磷酸化具有显著影响。乙醇消耗会导致线粒体基因组专门编码的必需多肽水平下降，这些多肽用于组装电子传递链（ETC）复合物。结果，它们的活性被抑制，ATP产生减少，对该现象的机制的研究揭示了乙醇引起的功能齐全的线粒体核糖体数量的减少（线粒体）沿着它们在分离时解离的趋势增加，这表明乙醇-线粒体多肽翻译水平的介导效应可能是能量损伤的潜在机制之一在酒精性肝病（ALD）的进展过程中观察到的代谢。线粒体核糖体的组装需要核编码蛋白和线粒体 编码核糖体RNA（rRNA）颗粒。它还需要rRNA内少量核苷酸的位点特异性甲基化，这是一个利用Adomet的过程。已发表的数据表明，慢性乙醇消耗导致细胞Adomet耗尽，这可能对核糖体组装产生重大影响。此外，我们小组的研究表明，对2岁雄性大鼠长期喂食乙醇14天导致电子传递链复合物I的活性显著降低，这可以通过与Adomet联合治疗来改善。拟议的研究将（a）研究rRNA甲基化对核糖体组装和功能的意义;（B）研究慢性乙醇喂养对rRNA甲基化的影响;（c）对线粒体rRNA甲基转移酶活性的影响。还将研究Adomet饲喂对（B）和（c）中研究的影响。希望这些分析将提供一个独特的见解线粒体蛋白质翻译的作用I ALD的进展。

DESCRIPTION (provided by applicant): It is proposed to investigate the hypothesis that chronic ethanol feeding results in decreased levels of hepatic S-adenosy-L-methionine (Adomet) and that this deficiency results in impaired mitochondrial ribosome assembly and depressed protein synthesis. Published data has demonstrated that ethanol has a pronounced effect upon oxidative phosphorylation in the liver. Ethanol consumption results in decreased levels of essential polypeptides encoded for: exclusively by the mitochondrial genome-that are utilized in the assembly of electron transport chain (ETC) complexes. As a consequence, their activities are depressed and ATP production decreases, investigations is to the mechanism(s) responsible for the phenomenon revealed an ethanol-elicited decrease in the number of fully functioning mitochondrial ribosomes (mitoribosomes) along with an increased tendency for them to dissociate upon isolation, This suggests that iethanol-mediated effects at the level of mitochondrial polypeptide translation may be one of the underlying imechanisms involved in the impairment of energy metabolism seen during the progression of alcoholic liver disease (ALD). Assembly of mitochondrial ribosomes requires nuclear encoded proteins and mitochondriaUy encoded ribosomal RNA (rRNA) particles. It also requires site-specific methylation of a small number of nucleotides within the rRNA, a process that utilizes Adomet. Published data has shown that chronic ethanol consumption results in depletion of cellular Adomet, which may have significant consequences for ribosome assembly. Further, studies from our group have shown that chronic ethanol-feeding to 2 year old male rats for 14 days results in a significant decrease in the activity of complex I of the electron transport chain and that this can be ameliorated by concomitant treatment with Adomet. The proposed studies will (a) investigate the significance of rRNA methylation upon ribosome assembly and function; (b) investigate the effect of chronic ethanol-feeding upon rRNA methylation; and (c) upon the activity of mitochondrial rRNA methyltransferases. The effect of Adomet feeding upon the studies in (b) and (c) will also be investigated. It is hoped that these analyses will provide a unique insight into the role of mitochondrial protein translation I the progression of ALD.