Words similar to hlh
Example sentences for: hlh
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An inhibitory effect of USF on Myc-mediated cellular proliferation has been demonstrated in HeLa cells [ 33 ] , and a non-canonical HLH element inhibits expression of the fibroblast growth factor binding protein (FGF-BP) in several carcinoma cells [ 34 ] . Furthermore, USF2 inhibits binding of hypoxia-inducible factor-1 (HIF-1) to the plasminogen activator inhibitor -1 (PAI-1) gene in hepatocytes in order to disturb transcriptional activation [ 35 ] . Our results add C/EBPβ-mediated activation of RIIβ to the mechanisms inhibited by USF.
Binding of truncated USF2 to a HLH element in the prostaglandin G/H synthase 2 (PGHS-2) promoter was abolished in extracts from cells stimulated by human chorionic gonadotrophin (hCG) which signals through cAMP [ 32 ] .
Among genes that are stimulated by FSH/cAMP during the period of maturation of Sertoli cells (15 to 20 days of age in rats), are several subunits of cAMP-dependent protein kinase (PKA), the serine/threonine kinase mainly responsible for the downstream effects of FSH [ 15 ] . Expression of the RIIβ regulatory subunit of cAMP-dependent protein kinase is highly induced (50-fold) at the mRNA level in primary cultures of rat Sertoli cells as a late response to cAMP peaking at 12 hours [ 16 ] . We have demonstrated that expression of CAAT/Enhancer binding protein β (C/EBPβ) is induced by cAMP with rapid kinetics in Sertoli cells, and that C/EBPβ is responsible for induction of late response genes like the RIIβ-gene [ 17 ] . The RIIβ promoter contains a conserved E-box/HLH element in the basal promoter localized at -280 to -275 relative to the functional ATG [ 18 ] . This element is shown to be important for cAMP-responsiveness in granulosa cells, and it has been shown to bind both USF and Myc in CHO and NB2a cells [ 18 19 ] . In this work, we show that USF isoforms may regulate cAMP responsiveness of the RIIβ promoter by modulating the effect of C/EBP, and that the formation of USF isoforms may be regulated by cAMP in Sertoli cells.
C; catalytic subunit, cAMP; cyclic adenosine monophosphate, CAT; chloramphenicol acetyl transferase, C/EBP; CAAT/enhancer binding protein, ChoRE; carbohydrate response element, CMV; cytalomega virus, 8-CPT-cAMP; 8-(4-chlorophenyl)thio-cAMP, CREB; cAMP-response element binding protein, EMSA; electrophoretic mobility shift assay, FAS; fatty acid synthase, FSH; follicle stimulating hormone, GIRE; glucose/insulin response element, hCG; human chorionic gonadotrophin, HLH; helix-loop-helix, IRE; insulin response element, MHC; major histocompability complex, PGHS; prostaglandin G/H synthase, PKA; cAMP-dependent protein kinase, R; regulatory subunit, USF; upstream stimulating factor, WB; Western blot.
Electrophoretic mobility shift assays (EMSAs) were performed using a double stranded [ 32P]-end-labeled oligonucleotide covering the consensus E-box/HLH element (underlined) and flanking sequences from the RIIβ promoter (-305, 5'-GATCGCCGGGTTGCCATGGTTT CCGGGGAT CACGTGGGCGCGCGG-3', -268).
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