Contribution of the hormone-response elements of the proximal ApoA-I promoter, ApoCIII enhancer, and C/EBP binding site of the proximal ApoA-I promoter to the hepatic and intestinal expression of the ApoA-I and ApoCIII genes in transgenic mice.
We have generated and studied the pattern of expression of transgenic mouse lines carrying the human apoA-I and apoCIII gene cluster mutated at different sites. In two lines, we have either mutated the hormone-response element (HRE) of element G of the apoCIII enhancer or the C/EBP binding site of the proximal apoA-I promoter. In a third line, we have mutated the two HREs of the apoA-I promoter and the HRE of the apoCIII enhancer. Mutations in the HRE of element G reduced the hepatic and intestinal expressions of the reporter chloramphenicol acetyltransferase (CAT) gene (which substituted the apoCIII gene) to 4 and 13% of the wild-type (WT) control, whereas the hepatic and intestinal expressions of the apoA-I gene were reduced to 92 and 25% of the WT control, respectively. A mutation in the C/EBP site increased the hepatic and intestinal expressions of the apoA-I gene approximately 1.25- and 1.6-fold, respectively, and did not affect the expression of the CAT gene. The mutation in the three HNF-4 binding sites of the apoA-I promoter/apoCIII enhancer nearly abolished the expression of apoA-I and the reporter CAT gene in all tissues. These findings establish the importance of the HREs for the hepatic and intestinal expressions of the apoA-I and apoCIII genes and suggest that C/EBP does not play a central role in the expression of the apoA-I gene.
Kan
Horng-Yuan
HY
Section of Molecular Genetics, Center for Advanced Biomedical Research, Boston University School of Medicine, 715 Albany Street, Boston, Massachusetts 02118-2394, USA.
Georgopoulos
Spiros
S
Zanni
Markella
M
Shkodrani
Adelina
A
Tzatsos
Alexandros
A
Xie
Hou Xiang
HX
Zannis
Vassilis I
VI
D000818:Animals; D016632:Apolipoprotein A-I / Q000235:genetics*; D053305:Apolipoprotein C-III; D001056:Apolipoproteins C / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004742:Enhancer Elements, Genetic; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D005810:Multigene Family; D009154:Mutation; D011401:Promoter Regions, Genetic; D020218:Response Elements; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D016632:Apolipoprotein A-I; D053305:Apolipoprotein C-III; D001056:Apolipoproteins C