REGULATION OF CYSTATHIONASE EXPRESSION

这项研究的长期目标是了解 哺乳动物细胞中的硫化作用。跨硫途径的结果 在蛋氨酸的硫原子转移到半胱氨酸中。最早的 该途径的酶与转甲基化途径共享，通过该途径 甲基对许多重要的新陈代谢有贡献 中间体。对分子机制几乎一无所知。 这是酶在这两种途径中表达的基础。 我们的具体目标是阐明 谷胱甘肽酶(CSE)的表达调控 硫化作用。我们将研究CSE对大鼠肝脏发育的调控， 这显示了与人类肝脏相似的CSE表达的时间模式。 CSE蛋白质合成和降解率将在不同的条件下测定 发展的各个阶段。功能性CSE mRNA的浓度将是 确定了每个阶段和大鼠脑组织的CSE活性 非常低。为了更详细地了解CSE的遗传调控， 我们将分离代表CSE mRNA的cdna克隆，使用我们的特异性 用于文库筛选和/或多聚体免疫选择的抗血清。使用 克隆的c DNA，我们将分析转录和转录后 CSE基因表达的调控及基因数目的确定 CSE基因的拷贝、内含子的存在和甲基化状态(S)。 有许多临床和基本问题与 转硫酶。出生时缺乏CSE可能会使半胱氨酸成为 新生儿必需的氨基酸。酶活性的遗传缺失 导致胱硫氨酸尿症，这与精神疾病有关 智力迟缓。通过硫化作用产生的肝细胞胞苷 对维持谷胱甘肽水平至关重要。这种硫醇是主要的。 保护细胞免受辐射和有毒药物的重要性，包括 对乙酰氨基酚和化疗药物。因此，对 对硫磺转化的监管可能会对 人类健康。(B)

The long-term objective of this research is to understand the regulation of transsulfuration in mammalian cells. The transsulfuration pathway results in the transfer of the sulfur atom of methionine into cysteine. The early enzymes of the path are shared with the transmethylation pathway by which methyl groups are contributed to a number of important metabolic intermediates. There is almost no knowledge of the molecular mechanisms which underlie expression of enzymes in either path. Our specific objectives are to elucidate the molecular mechanisms which regulate expression of cystathionase (CSE), the terminal enzyme of transsulfuration. We shall examine CSE regulation in developing rat liver, which shows a similar temporal pattern of CSE expression to human liver. CSE protein synthesis and degradation rates will be determined at different stages of development. The concentration of functional CSE mRNA will be ascertained for each stage and for rat brain tissue, where CSE activity is very low. To obtain more detailed understanding of CSE genetic regulation, we shall isolate cDNA clones representing CSE mRNA, employing our specific antisera for library screening and/or polysome immunoselection. Using the cloned cDNA, we shall analyze transcriptional and post-transcriptional regulation of CSE gene expression as well as determine the number of gene copies, presence of introns, and methylation states of the CSE gene(s). There are numerous clinical and basic problems that relate to transsulfuration enzymes. Absence of CSE at birth may make cysteine an essential amino acid for the neonate. Genetic absence of enzyme activity results in cystathioninuria which has been associated with mental retardation. The hepatic production of cyteine by transsulfuration is crucial in maintaining glutathione levels. This thiol is of major importance in protecting cells from radiation and toxic drugs including acetaminophen and chemotherapeutic agents. Thus, an understanding of the regulation of transsulfuration could have far reaching implications for human health. (B)