Dominant negative regulation by c-Jun of transcription of the uncoupling protein-1 gene through a proximal cAMP-regulatory element: a mechanism for repressing basal and norepinephrine-induced expression of the gene before brown adipocyte differentiation.
The brown fat uncoupling protein-1 (ucp-1) gene is regulated by the sympathetic nervous system, and its transcription is stimulated by norepinephrine, mainly through cAMP-mediated pathways. Overexpression of the catalytic subunit of protein kinase A stimulated a chloramphenicol acetyltransferase expression vector driven by the 4.5-kb 5'-region of the rat ucp-1 gene. Mutant deletion analysis indicated the presence of the main cAMP-regulatory element (CRE) in the proximal region between -141 and -54. This region contains an element at -139/-122 able to confer enhancer and protein kinase A (PKA)-dependent activity to the basal thymidine kinase promoter. The potency of this element was much higher in differentiated than in nondifferentiated brown adipocytes. Gel shift analyses indicated that a complex array of proteins from brown fat nuclei bind to the -139/-122 element, among which CRE-binding protein (CREB) and Jun proteins were identified. In transfected brown adipocytes, c-Jun was a negative regulator of basal and PKA-induced transcription from the ucp-1 promoter acting through this proximal CRE region. A double-point mutation in the -139/-122 element abolished both PKA- and c-Jun-dependent regulation through this site, and overexpression of CREB blocked c-Jun repression. Thus, an opposite action of these two transcription factors on the -139/-122 CRE is proposed. c-Jun content in brown adipocytes differentiating in culture correlated negatively with both ucp-1 gene expression and the acquisition of the brown adipocyte morphology. These findings indicate that c-Jun provides a molecular mechanism to repress the basal and cAMP-mediated expression of the ucp-1 gene before the differentiation of the brown adipocyte.
Yubero
P
P
Departament de Bioquímica i Biologia Molecular, Universitat de Barcelona, Spain.
Barberá
M J
MJ
Alvarez
R
R
Viñas
O
O
Mampel
T
T
Iglesias
R
R
Villarroya
F
F
Giralt
M
M
D017667:Adipocytes / Q000166:cytology; D002001:Adipose Tissue, Brown / Q000166:cytology*; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics*; D002454:Cell Differentiation; D000242:Cyclic AMP / Q000494:pharmacology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000502:physiology; D004742:Enhancer Elements, Genetic; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000187:drug effects*; D007473:Ion Channels; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D024101:Mitochondrial Proteins; D009638:Norepinephrine / Q000494:pharmacology*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins; D012045:Regulatory Sequences, Nucleic Acid; D014162:Transfection; D000071256:Uncoupling Protein 1
D002352:Carrier Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D016755:Proto-Oncogene Proteins c-jun; D011993:Recombinant Fusion Proteins; C000604372:Ucp1 protein, mouse; C000604373:Ucp1 protein, rat; D000071256:Uncoupling Protein 1; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D009638:Norepinephrine