Molecular Dissection of a Heme Regulatory Complex in the Yeast Saccharomyces Cerevisiae

点击翻译按钮获取中文摘要

9617472 Zhang Eukaryotic cells require heme to use and sense oxygen, to generate cellular energy by respiration, and to synthesize and degrade lipids, steroids and related compounds. In addition to its role as a prosthetic group in enzymes, cytochromes and globins, heme acts directly as a regulator of cellular and molecular systems that use or sense oxygen, and controls the growth and differentiation of a wide array of cells in mammals. The goal of this research is the molecular dissection of the heme regulatory complex in yeast. The yeast Saccharomyces cerevisiae is the only eukaryote in which a master regulator of heme signaling, heme activating protein-1 (HAP1), has been identified and cloned. In response to heme, HAP1 activates transcription of genes encoding respiratory functions and functions required for controlling oxidative damage. In the absence of heme, HAP1 is sequestered in a high molecular weight complex with certain other cellular factors. This research will test the hypothesis that the binding of heme to HAP1 changes the conformation of HAP1 causing it to dissociate from the high molecular weight complex and subsequently bind to DNA with high affinity and activate transcription. Both mutational and biochemical analyses, including the development of a heme-responsive in vitro transcription system, will be used to characterize the specific interaction of heme with HAP1, the interaction of HAP1 with other cellular factors in the high molecular weight complex, and the mechanism by which HAP1 dissociation from the high molecular weight complex mediates heme regulation of transcription. By unraveling the mechanism governing the heme-HAP1 induction pathway in yeast, this research will provide the first molecular description of how a regulatory complex mediates heme action in eukaryotic cells, and will lay the basis for understanding heme regulation of fundamental molecular and cellular processes in higher eukaryotic cells. Eukaryotic cells require heme to use and sense oxy gen, to generate cellular energy by respiration, and to synthesize and degrade lipids, steroids and related compounds. In addition to its role as a prosthetic group in enzymes, cytochromes and globins, heme acts directly as a regulator of cellular and molecular systems that use or sense oxygen, and controls the growth and differentiation of a wide array of cells in mammals. By unraveling the heme induction pathway in yeast, this research will provide the first molecular description of how a heme regulatory complex mediates heme action in eukaryotic cells, and will lay the basis for understanding heme regulation of fundamental molecular and cellular processes in higher eukaryotic cells.