Prokaryotic gene regulation by light and oxygen

描述(由申请人提供)：氧分压的改变会影响所有细胞类型的基因表达。在细菌系统中，氧气调节与有氧和无氧能量代谢相关的各种基因。新陈代谢过程，如固碳、固氮、呼吸和光合作用，在有氧或无氧的情况下进行调节。在酵母和藻类细胞中，氧已知会影响氧化防御基因和代谢酶的转录。在哺乳动物细胞中，已知有越来越多的基因受氧调控，如血管生长因子，它们是从现有血管合成新的毛细血管的关键调节因子。除了生理作用外，这些生长因子还参与疾病过程，如在肿瘤生长过程中刺激毛细血管形成。这项建议的核心是阐明细菌胶囊红杆菌和球形红杆菌如何能够感知氧分压的变化，并相应地改变基因表达的分子细节。这些相关物种能够以各种能量产生方式生长，包括好氧呼吸、厌氧发酵和光合作用。参与上述每个过程的基因的表达都会受到氧分压变化和光照强度变化的影响。光对细胞生理的调节也已知发生在从细菌到哺乳动物的许多生物体中，这是这一提议研究的第二个过程。事实上，本研究中研究的一个关键的氧调节转录因子也受到光强度的调节。作为研究氧和光对基因表达调控的模型系统，我们重点研究了四吡咯的生物合成过程。这一途径受到氧气和光照强度的高度调控，并负责B12、血红素和叶绿素等重要代谢物的产生。

DESCRIPTION (provided by applicant): Alteration in oxygen tension affects gene expression in all cell types. In bacterial systems, oxygen regulates a variety of genes involved in aerobic versus anaerobic energy metabolism. Metabolic processes such as carbon fixation, nitrogen fixation, respiration and photosynthesis are regulated in response to the presence or absence of oxygen. In yeast and algal cells, oxygen is known to affect transcription of oxidative defense genes as well as metabolic enzymes. In mammalian cells, a growing number of genes are known to be oxygen regulated such as vascular growth factors that are key regulators for the synthesis of new capillary sprouts from preexisting vessels. Besides physiological roles, these growth factors are involved in disease processes such as the stimulation of capillary formation during tumor growth. This proposal is centered on elucidating molecular details of how bacteria Rhodobacter capsulatus and Rhodobacter sphaeroides are able to sense changes in oxygen tension, and in response, alter gene expression. These related species are capable of growth in a variety of energy generating modes including aerobic respiration, anaerobic fermentation and photosynthesis. The expression of genes involved in each of these processes are affected by alterations in oxygen tension, as well as by variations in light intensity. Regulation of cell physiology by light is also known to occur in a number of organisms ranging from bacterial to mammals and is a second process that is studied by this proposal. Indeed, one of the key oxygen regulated transcription factors studied in this proposal is also regulated by light intensity. As a model system for studying both oxygen and light regulation of gene expression, we have focused on the process of tetrapyrrole biosynthesis. This pathway is highly regulated by oxygen and light intensity and is responsible for the production of such important metabolites as B12, heme and chlorophylls.