Regulation in vitro of an L-CAM enhancer by homeobox genes HoxD9 and HNF-1.
Previous studies have shown that in vitro expression of the neural cell adhesion molecule (N-CAM) can be regulated by the products of homeobox genes HoxB9, -B8, and -C6. N-CAM is a Ca(2+)-independent immunoglobulin-related CAM that plays an important role in neural development. In the present study, we investigated whether the liver cell adhesion molecule (L-CAM) a member of the Ca(2+)-dependent CAM family (cadherins) is also regulated by homeobox-containing genes. In transient cotransfection experiments of NIH 3T3 cells, we observed that both HoxD9 and liver-enriched POU-homeodomain transcription factor, HNF-1, activated chloramphenicol acetyltransferase gene reporter constructs containing the L-CAM promoter and an enhancer present in the second intron of the chicken L-CAM gene. Using electrophoretic mobility-shift assays, we found that components of cell extracts from NIH 3T3 cells transfected with HoxD9 bound to a small region of the L-CAM enhancer having a consensus sequence that is a putative binding site for HNF-1. Components of extracts from the chicken hepatoma cell line LMH that had been transfected with an HNF-1 expression vector also bound to this same site. In nuclear run-on experiments with nuclei from LMH cells that were transfected with expression vectors for HoxD9 or HNF-1, L-CAM RNA levels were increased 33-fold and 4-fold respectively. Using the same run-on procedure, it was confirmed that nuclei prepared from normal embryonic chicken liver cells expressed the RNAs for HoxD9, HNF-1, and L-CAM. Taken together with previous observations, these data raise the possibility that homeobox-containing genes will have a widespread role in the place-dependent expression of CAMs belonging both to immunoglobulin-related and to cadherin families.
Goomer
R S
RS
Department of Neurobiology, Scripps Research Institute, La Jolla, CA 92037.
Holst
B D
BD
Wood
I C
IC
Jones
F S
FS
Edelman
G M
GM
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015820:Cadherins / Q000096:biosynthesis* / Q000235:genetics* / Q000302:isolation & purification; D002645:Chickens; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000235:genetics*; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D005801:Genes, Homeobox; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D007438:Introns; D008099:Liver / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics*; D009687:Nuclear Proteins; D015345:Oligonucleotide Probes; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics*; D014162:Transfection
D015820:Cadherins; D004268:DNA-Binding Proteins; D051538:Hepatocyte Nuclear Factor 1-alpha; C496488:Hnf1a protein, mouse; C496496:Hnf1b protein, mouse; C490282:Hoxd9 protein, mouse; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D015345:Oligonucleotide Probes; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta