Regulation of the Dictyostelium glycogen phosphorylase 2 gene by cyclic AMP.
A crucial developmental event in the cellular slime mold, Dictyostelium discoideum, is glycogen degradation. The enzyme that catalyzes this degradation, glycogen phosphorylase 2 (gp-2), is developmentally regulated and cAMP appears to be involved in this regulation. We have examined several aspects of the cAMP regulation of gp-2. We show that addition of exogenous cAMP to aggregation competent amoebae induced the appearance of gp-2 mRNA. The induction of gp-2 mRNA occurred within 1 and 1.5 h after the initial exposure to cAMP. Exposure to exogenous cAMP concentrations as low as 1.0 microM could induce gp-2 mRNA. We also examined the molecular mechanism through which cAMP induction of gp-2 occurs. Induction of gp-2 appears to result from a mechanism that does not require intracellular cAMP signaling, and may occur directly through a cAMP binding protein without the requirement of any intracellular signalling. We also examined the promoter region of the gp-2 gene for cis-acting elements that are involved in the cAMP regulation of gp-2. A series of deletions of the promoter were fused to a luciferase reporter gene and then analyzed for cAMP responsiveness. The results indicated that a region from -258 nucleotides to the transcriptional start site is sufficient for essentially full activity and appears to carry all necessary cis-acting sites for cAMP induction. Further deletion of 58 nucleotides from the 5' end, results in fivefold less activity in the presence of cAMP. Deletion of the next 104 nucleotides eliminates the cAMP response entirely.
Sucic
J F
JF
Biology Department, Virginia Polytechnic Institute and State University, Blacksburg 24061.
Selmin
O
O
Rutherford
C L
CL
D000818:Animals; D001483:Base Sequence; D003994:Bucladesine / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D004023:Dictyostelium / Q000187:drug effects / Q000235:genetics*; D004790:Enzyme Induction / Q000187:drug effects; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D006005:Phosphorylases / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012331:RNA, Fungal / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D017384:Sequence Deletion; D015398:Signal Transduction / Q000502:physiology
D005656:Fungal Proteins; D012331:RNA, Fungal; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C018892:2'-deoxy cyclic AMP; D002110:Caffeine; D003994:Bucladesine; D000242:Cyclic AMP; D008156:Luciferases; D006005:Phosphorylases