%0 Journal Article
%T USF2 inhibits C/EBP-mediated transcriptional regulation of the RII¦Â subunit of cAMP-dependent protein kinase
%A Maria Dahle
%A Kjetil Task¨¦n
%A Kristin Task¨¦n
%J BMC Molecular Biology
%D 2002
%I BioMed Central
%R 10.1186/1471-2199-3-10
%X In this work we show that USF1, USF2 and truncated USF isoforms bind to a conserved E-box in the RII¦Â gene. Interestingly, overexpression of USF2, but not USF1, led to inhibition of both cAMP- and C/EBP¦Â-mediated induction of RII¦Â. Furthermore, Western blots show that a novel USF1 isoform is induced by cAMP in Sertoli cells.These results indicate that the expression of various USF isoforms may be regulated by cAMP, and that the interplay between USF and C/EBP¦Â is important for cAMP-mediated regulation of RII¦Â expression. The counteracting effects of USF2 and C/EBP¦Â observed on the RII¦Â promoter is in accordance with the hypothesis that C/EBP and USF play opposite roles in regulation of glucose metabolism.Follicle stimulating hormone (FSH) regulates spermatogenesis through the somatic Sertoli cells of the testis [1]. Sertoli cells act as "nursing" cells and supplies germ cells with energy and controls the biochemical environment in which they develop [2]. Among the FSH-regulated functions are increased glucose uptake and oxidation. In response to glucose, transcription of several glycolytic and lipogenic genes are activated through the glucose/carbohydrate/insulin response element (GIRE, ChoRE or IRE) [3,4]. Upstream stimulatory factors (USF) 1 and 2 are characterized by a basic/helix loop helix/leucine zipper domain responsible for dimerization and DNA binding, and are major components of the GIRE complex [5-8].The main USF isoforms USF1 (43 kDa) and USF2 (44 kDa) are ubiquitously expressed and encoded by separate genes [9-11]. In addition, more isoforms of USF2 are produced due to alternative splicing and utilization of different translation start sites [12,13]. USF factors exist as homo and heterodimers, and the heterodimer of USF1/USF2a seems to dominate, although there are cell-type specific variations [12]. USF1 and USF2 show different transactivating potential, and USF2 appears to be the functional transactivator of the GIRE complex, although both USF1 and USF
%U http://www.biomedcentral.com/1471-2199/3/10