Role of USF1 and USF2 as potential repressor proteins for human intestinal monocarboxylate transporter 1 promoter.
Butyrate, a short-chain fatty acid, is the major energy fuel for the colonocytes. We have previously reported that monocarboxylate transporter isoform 1 (MCT1) mediates uptake of butyrate by human colonic Caco-2 cells. To better understand the mechanisms of MCT1 expression and regulation in the human intestine, we examined the activity and regulation of MCT1 promoter in Caco-2 cells. The transcription initiation site in the MCT1 promoter was identified as a guanine nucleotide 281 bp upstream from the translation initiation site and is surrounded by a guanine-cytosine-rich area. The promoter was found to be highly active when transfected into Caco-2 cells, and its activity decreased with deletions at its 5'-end. Gel mobility shift experiments showed binding of the transcription factors upstream stimulatory factor (USF)1 and 2 to the site -114 to -119 of the MCT1 promoter. With the use of site-directed mutagenesis and promoter activity in Caco-2 cells, the USF proteins appeared to have a repressor role on the MCT1 promoter, which was further confirmed by cotransfecting expression vectors encoding USF1 and 2 in Caco-2 cells and determining endogenous MCT1 expression in USF2 overexpressed cells. The two potential SP1 binding sites found in the same region of the promoter were found not to be involved in its regulation.
Hadjiagapiou
Christos
C
Univ. of Illinois at Chicago, Medical Research Service (600/151 Jesse Brown VA Medical Center, 820 South Damen Ave., Chicago, IL 60612, USA.
Borthakur
Alip
A
Dahdal
Refka Y
RY
Gill
Ravinder K
RK
Malakooti
Jaleh
J
Ramaswamy
Krishnamurthy
K
Dudeja
Pradeep K
PK
D001483:Base Sequence; D002087:Butyrates / Q000378:metabolism; D018938:Caco-2 Cells; D004268:DNA-Binding Proteins / Q000494:pharmacology*; D020869:Gene Expression Profiling; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D016350:Leucine Zippers; D008969:Molecular Sequence Data; D027501:Monocarboxylic Acid Transporters / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D027981:Symporters / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology; D014157:Transcription Factors / Q000494:pharmacology*; D014162:Transfection; D051720:Upstream Stimulatory Factors; D000099233:Monocarboxylate Transport Protein 1
D002087:Butyrates; D004268:DNA-Binding Proteins; D027501:Monocarboxylic Acid Transporters; D027981:Symporters; D014157:Transcription Factors; D051720:Upstream Stimulatory Factors; D000099233:Monocarboxylate Transport Protein 1; C497181:USF1 protein, human; C497184:USF2 protein, human