Regulation of apo A-IV transcription by lipid in newborn swine is associated with a promoter DNA-binding protein.
Dietary lipid acutely upregulates apolipoprotein (apo) A-IV expression by sevenfold at the pretranslational level in neonatal swine jejunum. To determine the mechanism of this regulation, two-day-old female swine received intraduodenal infusions of low- and high-triacylglycerol (TG) isocaloric diets for 24 h. Nuclear runoff assay confirmed apo A-IV gene transcriptional regulation by the high-TG diet. Footprinting analysis using the swine apo A-IV proximal promoter sequence (+14 to -246 bp) demonstrated three regions protected by the low-TG extracts. Of these three motifs, only ACCTTC showed 100% homology to the human sequence and was further studied. EMSA was performed using probes containing wild-type (WT) and mutant (M) motifs. A shift was noted with the low-TG nuclear extracts with the WT probe but not with the M probe. Excess unlabeled free WT probe competed out the shift, whereas the M probe did not. No significant shift occurred with either probe using high-TG extracts. These results suggest that a repressor protein binds to the ACCTTC motif and becomes unbound during lipid absorption, allowing transcriptional activation of the apo A-IV gene in newborn swine small intestine.
Lu
Song
S
Children's Foundation Research Center of Memphis at Le Bonheur Children's Medical Center, University of Tennessee Health Science Center, Memphis, Tennessee 38103, USA.
Yao
Ying
Y
Wang
Heng
H
Meng
Songmei
S
Cheng
Xiangying
X
Black
Dennis D
DD
D000199:Actins / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001054:Apolipoproteins A / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics*; D003850:Deoxyribonuclease I / Q000378:metabolism; D004032:Diet; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D008055:Lipids / Q000502:physiology*; D008969:Molecular Sequence Data; D023282:Nuclease Protection Assays; D009841:Oligonucleotides / Q000235:genetics; D011247:Pregnancy; D011401:Promoter Regions, Genetic / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013552:Swine
D000199:Actins; D001054:Apolipoproteins A; D004268:DNA-Binding Proteins; D008055:Lipids; D009841:Oligonucleotides; C022205:apolipoprotein A-IV; D003850:Deoxyribonuclease I