Upstream stimulatory factor proteins are major components of the glucose response complex of the L-type pyruvate kinase gene promoter.
L-type pyruvate kinase (L-PK) gene transcription is induced by glucose through its glucose response element (GlRE) composed of two degenerated E boxes able to bind in vitro ubiquitous upstream stimulator factor (USF) proteins. Here we demonstrate in vivo, by transient transfections in hepatoma cells, that (i) native USF proteins synthesized from expression vectors can act as transactivators of the L-PK promoter via the GlRE, stimulating transcription without glucose and, therefore, decreasing the glucose responsiveness of the promoter; (ii) expression of the truncated USF proteins, able to bind the GlRE but devoid of the NH2-terminal activation domain, represses the activation of the L-PK promoter by glucose; and (iii) a similar repression of the glucose effect is observed upon expression of mutant USF proteins devoid of the basic DNA binding domain, able to dimerize with endogenous USF but not to bind the GlRE. We conclude that USF proteins are components of the transcriptional glucose response complex assembled on the L-PK gene promoter.
Institut Cochin de génétique Moléculaire, U.129 INSERM, Université René Descartes, Paris, France.
A M
AM
Lefrançois-Martinez
A
A
Martinez
B
B
Antoine
M
M
Raymondjean
A
A
Kahn
D001483:Base Sequence; D004268:DNA-Binding Proteins; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D011770:Pyruvate Kinase / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D051720:Upstream Stimulatory Factors
D004268:DNA-Binding Proteins; D009838:Oligodeoxyribonucleotides; D014157:Transcription Factors; C497181:USF1 protein, human; D051720:Upstream Stimulatory Factors; D011770:Pyruvate Kinase; D005947:Glucose