MOLECULAR ANALYSIS OF THE DISTAL ENHANCER OF THE MOUSE ALPHA-FETOPROTEIN GENE

Citation
Jh. Millonig et al., MOLECULAR ANALYSIS OF THE DISTAL ENHANCER OF THE MOUSE ALPHA-FETOPROTEIN GENE, Molecular and cellular biology, 15(7), 1995, pp. 3848-3856
Citations number
51
Categorie Soggetti
Biology
ISSN journal
02707306
Volume
15
Issue
7
Year of publication
1995
Pages
3848 - 3856
Database
ISI
SICI code
0270-7306(1995)15:7<3848:MAOTDE>2.0.ZU;2-3
Abstract
The mouse alpha-fetoprotein (AFP) gene is transcribed at high levels i n the visceral endoderm of the yolk sac and fetal liver and at much lo wer rates in the endoderm of the fetal gut. Expression of the gene in vivo requires the presence of at least one of three enhancers which li e in its 5' flanking region. In this report, we establish that the mos t distal AFP enhancer directed consistent expression of a linked AFP m inigene in all three endodermal tissues in transgenic mice. The enhanc er is composed of three domains, each of which is essential for full e nhancer function by transient transfection assays. DNase I footprintin g identified three regions of the enhancer which are protected by huma n hepatoma nuclear extracts, one of which corresponded to a consensus site for HNF-3 binding. Site-directed mutations in this site caused a 10-fold reduction in enhancer function by transient transfection. In t ransgenic mice, however, the mutation resulted in sporadic expression of the transgene, dependent on the site of integration. A similar acqu isition of position-dependent sporadic expression of the transgene was observed with a mutation in a second protein binding site, despite th e fact that this mutation had very little effect on enhancer function as assessed by transient transfection. These studies underscore the va lue of examining the functions of specific protein binding sites in vi vo.