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

Abstract

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.

Transcription Factors Bind Negatively Selected Sites within Human mtDNA Genes

“…Notably, the identified TFs (c-Jun, Jun-D, and CEBPb) are well-known modulators of nDNA-encoded genes, among which are those encoding proteins that are imported into the mitochondria where they are important for mitochondrial function (Brady et al 1992; Xia et al 1998; Yubero et al 1998; Tsuji 2005). As transcriptional coexpression of genes coding for components of the OXPHOS system was identified in different tissues (van Waveren and Moraes 2008; Garbian et al 2010), our findings lend further support to the thought that mitonuclear coregulation is plausible (Bar-Yaacov et al 2012).…”

Uncoupling Protein 1 of Brown Adipocytes, the Only Uncoupler: A Historical Perspective

“…This region is able to bind transcriptional factors such as CREB, CCAAT/enhancer binding proteins α and β, jun, Ets1, thyroid hormone receptors, retinoid X-receptor, and PPARs. Other important regions, in particular cAMP-response elements, were also identified outside of the enhancer region and in the promoter region (Cassard-Doulcier et al, 1994; Kozak et al, 1994; Yubero et al, 1994, 1998; Alvarez et al, 1995; Silva and Rabelo, 1998; Rim and Kozak, 2002; Xue et al, 2005). Xue et al (2005) proposed that small variations in the levels of several transcriptional components of the Ucp 1 enhanceosome interact synergistically to achieve large differences in Ucp 1 expression.…”

PPARs in the Control of Uncoupling Proteins Gene Expression

“…The 5′-flanking regions of the rat, mouse, and human UCP1 genes share a common genomic structure: a proximal regulatory region and an upstream enhancer located at −2 kb for review, see [17]. The proximal regulatory promoter contains C/EBP-regulated sites and the main cAMP-regulatory element [14, 18, 19]. The UCP1 gene distal enhancer includes a complex organization of nuclear receptor binding sites which mediate the transcriptional activation of the UCP1 gene by retinoids, thyroid hormones, PPAR agonists, and also cAMP, probably through induction of the PPAR coactivator-1 α (PGC-1 α ) [18, 20–25].…”