RAS GENES AND REGULATION OF CELLULAR MORPHOGENESIS

本项目将研究ras蛋白在 真核细胞生长发育的调控。丝状的 真菌，总状毛霉，被诱导经历三种特征类型 细胞形态发生的变化以响应生长条件的变化， 营养物质或气体环境，并提供了一个简单的模型系统 真核细胞发育，服从生化和遗传 分析。3个毛霉ras基因(MRAs)的累积mrna水平有 在细胞发育的几个不同阶段进行了分析。其中两个 基因MRAS1和MRAS3在细胞内差异表达 在这种真菌中的发展表明这些基因在 发育过程。例如，MRAS3基因几乎表达了 仅在无性孢子形成期间表达，而MRAS1的表达最高 “快速”分裂的菌丝细胞或转化为菌丝的细胞的水平。 MRAS1和MRAS3基因具有独特的时间表达模式， 可能表明它们在儿童的生长发育中扮演着不同的角色。 有机体。根据核苷酸序列分析，由 MRAS基因在氨基酸序列和大小上与H-S基因高度相似。 参与调控的高等真核生物的RAS基因 细胞的生长和分化。因为这种蛋白质的相似性， 了解ras在细胞调控中的作用 在这些简单的真核细胞中的分化可能导致重要的 对这些细胞的增殖、分化和功能障碍的见解 发生在哺乳动物肿瘤中的过程。 这项研究提案的具体目的是：1)表征 Ras基因家族(MRAS)在总状花序中的表达；2)改变 利用MRAS基因在总状根霉菌中正常表达ras基因 载体；3)研究MRAS基因表达变化的影响 形态发生、细胞增殖和生物化学变化 在总状花序中伴随着这些过程。 正常的ras表达和蛋白活性将通过转化而改变。 带有设计用来改变MRAS蛋白的质粒构建的毛囊细胞 表达的结构、数量和时间模式。直接 观察将检测到形态发生反应的表型变化或 生长速度，而生化分析将被用来衡量影响 CAMP代谢和/或磷脂酰肌醇中ras表达的改变 新陈代谢。

This project will investigate the proposed role of ras proteins in regulation of growth and development of eukaryotic cells. The filamentous fungus, Mucor racemosus, is induced to undergo three characteristic types of cellular morphogenesis in response to changes in growth conditions, nutrients, or gaseous environment and provides a simple model system of eukaryotic cell development which is amenable to biochemical and genetic analysis. The accumulated mRNA levels of 3 Mucor ras genes (MRAS) have been analyzed during several different stages of cell development. Two of the genes, MRAS1 and MRAS3 are differentially expressed during cell development in this fungus suggesting that these genes play a role in the developmental processes. The MRAS3 gene for example is expressed almost exclusively during asexual sporulation, while MRAS1 is expressed at highest levels in "rapidly" dividing hyphal cells or cells converting to hyphae. The MRAS1 and MRAS3 genes have unique temporal patterns of expression which may suggest that they play different roles in growth and development of the organism. Based on nucleotide sequence analyses, the proteins encoded by the MRAS genes are highly similar in amino acid sequence and size to the H- ras gene of higher eukaryotes which has been implicated in the regulation of cell growth and differentiation. Because of this protein similarity, understanding of ras function in regard to regulation of cell differentiation in these simple eukaryotic cells may lead to important insights into cell proliferation, differentiation and malfunctions in these processes which occur in mammalian tumors. The specific aims of this research proposal are: 1) to characterize the expression of the ras gene family (MRAS) in M. racemosus; 2) to alter the normal expression patter of ras genes in M. racemosos using MRAS expression vectors; 3) to characterize the effects of altered MRAS expression on morphogenesis, cell proliferation, and the biochemical changes which accompany these processes in M. racemosus. Normal ras expression and protein activity will be altered by transforming Mucor cells with plasmid constructs designed to alter MRAS protein structure, quantity, and temporal pattern of expression. Direct observation will detect phenotypic changes in the morphogenetic response or growth rates, while biochemical assays will be used to measure the effects of altered ras expression on cAMP metabolism and/or phosphoinositid metabolism.