Developmental and cAMP-mediated regulation of glycogen phosphorylase 1 in Dictyostelium discoideum.
The Dictyostelium discoideum glycogen phosphorylase-1 (gp-1) exhibits a complex pattern of developmental expression in which differential temporal regulation of enzyme activity, protein levels and mRNA levels is observed. This pattern of expression implies that gp-1 regulation occurs at multiple levels, probably involving both transcriptional and post-transcriptional events. Post-translational control of gp-1 activity, in effect, actually regulates the protein from a developmental perspective. In this report we have examined several facets of this regulation. We show that addition of exogenous cAMP to cells in suspension culture caused changes in gp-1 enzyme activity and mRNA levels that are identical to those observed during normal development, suggesting that cAMP is involved in the regulation of gp-1. Exogenous cAMP could regulate gp-1 mRNA expression at concentrations as low as 1.0 microM. cAMP regulation of gp-1 mRNA appeared to occur through a mechanism that required intracellular cAMP signalling. We identified regions of the promoter necessary for gp-1 expression by using gp-1 promoter deletions to drive the expression of a luciferase reporter gene. Results of these experiments suggested that developmental and cAMP-mediated changes in gp-1 mRNA levels were the result of alterations in transcription. The promoter analysis also suggested that a vegetative specific element is located between -785 and -1894 nucleotides from the transcriptional start site. Elements necessary for maximal developmental and cAMP-mediated expression appear to be located between -1153 and -1894 nucleotides from the cap site. Sequence elements located between -180 and -1153 appear to be required for a basal level of late developmental expression.
Sucic
J F
JF
Biology Department, Virginia Polytechnic Institute and State University, Blacksburg 24061.
Luo
S
S
Williamson
B D
BD
Yin
Y
Y
Rogers
P V
PV
Rutherford
C L
CL
D000818:Animals; D001483:Base Sequence; D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D004271:DNA, Fungal / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D004023:Dictyostelium / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D017125:Genes, Protozoan; D017930:Genes, Reporter; D008156:Luciferases / Q000235:genetics; D008969:Molecular Sequence Data; D006005:Phosphorylases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016053:RNA, Protozoan / Q000235:genetics / Q000378:metabolism
D004271:DNA, Fungal; D016054:DNA, Protozoan; D012331:RNA, Fungal; D012333:RNA, Messenger; D016053:RNA, Protozoan; D000242:Cyclic AMP; D008156:Luciferases; D006005:Phosphorylases