Regulation of glycogen phosphorylase genes in Dictyostelium discoideum

dc.contributor.authorSucic, Joseph F.en
dc.contributor.committeechairRutherford, Charles L.en
dc.contributor.committeememberFalkinham III, Joseph O.en
dc.contributor.committeememberGregory, Eugene M.en
dc.contributor.committeememberJohnson, John L.en
dc.contributor.committeememberRogers, Patricia V.en
dc.description.abstractThe cellular slime mold, Dictyostelium discoideum, provides an ideal model system to study eukaryotic development, cell differentiation, and aging. A crucial developmental event in Dictyostelium is glycogen degradation. The degradation of glycogen provides glucose monomers that are used to synthesize structural components necessary for cellular differentiation. Glycogen degradation is catalyzed by glycogen phosphorylase, and two developmentally regulated glycogen phosphorylase activities have been discovered in Dictyostelium. Glycogen phosphorylase 1 (gp-1) activity is predominant early in development, and is dependent upon 5’ AMP as a positive allosteric modifier; glycogen phosphorylase 2 (gp-2) activity peaks late in development and is independent of 5° AMP. I showed that these two glycogen phosphorylase activities are associated with unique proteins that are the products of two distinct, but related, genes. Both genes were observed to be typical Dictyostelium genes in a number of respects. The gp-1 and gp-2 enzymes were also found to be similar to glycogen phosphorylases from other organisms. I also examined the developmental expression of these genes and found that both mRNAs are developmentally regulated; gp-1 mRNA levels fluctuate during development, while gp-2 mRNA levels increase late in development. The expression of the gp-1 and gp-2 genes is regulated by exogenous cAMP. Exogenous cAMP enhances the level of gp-1 mRNA, apparently through a mechanism that requires intracellular cAMP signaling. Specific DNA sequence elements appear to be required for maximal vegetative and late developmental expression of gp-1. Exogenous cAMP induces the appearance of gp-2 mRNA via a mechanism that appears to be independent of intracellular cAMP signaling. Repeated TA-rich sequences located between nucleotides 193 and 305 upstream of the transcriptional start site are necessary for maximal cAMP induction of gp-2. I also examined the cell type specific expression of gp-1 and gp-2. gp-1 is expressed predominantly in pre-stalk cells. gp-2 1s expressed in both cell types in a temporally regulated fashion; this type of expression has not been reported for other Dictyostelium genes, but, given the importance of glycogen degradation in both stalk and spore cells, it is not inconceivable that such regulation 1s necessary.en
dc.description.degreePh. D.en
dc.format.extentxii, 118 leavesen
dc.publisherVirginia Techen
dc.relation.isformatofOCLC# 27379405en
dc.rightsIn Copyrighten
dc.subject.lccLD5655.V856 1992.S835en
dc.subject.lcshDictyostelium discoideum -- Geneticsen
dc.subject.lcshGenetic regulationen
dc.subject.lcshGlycogen phosphorylase -- Genetic aspectsen
dc.titleRegulation of glycogen phosphorylase genes in Dictyostelium discoideumen
dc.type.dcmitypeTexten Polytechnic Institute and State Universityen D.en


Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
20.54 MB
Adobe Portable Document Format