An estrogen-responsive element derived from the 5' flanking region of the Xenopus vitellogenin A2 gene functions in transfected human cells

In the human breast cancer cell line MCF-7, we observe estrogen induction of the stable transfected Xenopus vitellogenin A2 gene. An estrogen-responsive element (ERE) could be defined by using a vitellogenin-chloramphenicol acetyltransferase hybrid gene in transient transfection experiments. The ERE is located in the 5' flanking region and is able to confer estrogen inducibility to the thymidine kinase gene promoter. By 5' and 3' deletions we have determined a 35 bp sequence sufficient for high stimulation by estradiol. Even 18 bp give a small estrogen response. The 35 bp ERE contains the palindromic sequence 5'GGTCACAGTGACC-3' as an essential element. The fact that the ERE of a frog gene functions in human cells demonstrates that signals and factors involved in the control have been conserved during evolution.     

N6-methyldeoxyadenosine residues at specific sites decrease the activity of the E1A promoter of adenovirus type 12 DNA

The activity of eukaryotic promoters is highly sensitive to site-specific modifications by DNA methylations. We have used the E1A promoter of adenovirus type 12 (Ad12) DNA to investigate the effects of methylations at different promoter sites on its activity. The chloramphenicol acetyltransferase gene has served as an activity indicator. Activity of the E1A promoter is lost or markedly decreased by deoxycytidine methylation of two HpaII (5'-C-C-G-G-3') or seven HhaI (5'-G-C-G-C-3') sites upstream from the 3' located T-A-T-A signal. There are two T-A-T-A signals in the E1A promoter of adenovirus type 12 DNA, one T-A-T-T-A-T sequence starting at nucleotide 276 (5' located), a second T-A-T-T-T-A-A sequence starting at nucleotide 414 (3' located). Deoxycytidine methylations at two AluI (5'-A-G-C-T-3') sites downstream from the 5' located T-A-T-A signal have no effect on promoter activity. When one EcoRI (5'-G-A-A-T-T-C-3') or one TaqI (5'-T-C-G-A-3') sequence at 281 base-pairs upstream or 61 base-pairs downstream from the 5' located E1A T-A-T-A signal, respectively, is deoxyadenosine methylated, the promoter becomes inactive. Deoxyadenosine methylation at one MboI (5'-G-A-T-C-3') site, which is located 127 nucleotides downstream from the 5' located T-A-T-A signal, fails to decrease E1A promoter activity. There is no conspicuous anatomical relation of any of these sites to the two presumptive enhancer sequences in the E1A promoter. We conclude that 5-deoxymethylcytidine or N6-methyldeoxyadenosine residues have to be introduced at highly specific promoter sites to inactivate the promoter. These sites are probably different for different promoters.     

Structural organization of the bovine thyroglobulin gene and of its 5'-flanking region

The structural organization of the bovine thyroglobulin gene has been investigated by a combination of Southern genomic blotting and direct analysis of cloned gene fragments isolated from a chromosomal DNA library. The entire locus is spread over more than 200,000 base pairs which makes it one of the largest eukaryotic genes studies to date. The coding information is scattered into at least 42 exons, 34 of which have been precisely identified. A different evolutionary origin of the 5' and 3' regions of the gene is supported by the highly different proportion of exonic material they contain (12% and 3%, respectively) and by the existence of sequence homology between the 3' region of thyroglobulin and acetylcholinesterase. Detailed sequence analysis of the 5' region of the gene and its flanking segment demonstrated that a significant homology exists between bovine and human thyroglobulin sequences, except for the presence within the ruminant promoter region of a 220-base-pair sequence belonging to the bovine monomer repeated family.     

Common variations in noncoding regions of the human natriuretic peptide receptor A gene have quantitative effects

Genetic susceptibility to common conditions, such as essential hypertension and cardiac hypertrophy, is probably determined by various combinations of small quantitative changes in the expression of many genes. NPR1, coding for natriuretic peptide receptor A (NPRA), is a potential candidate, because NPRA mediates natriuretic, diuretic, and vasorelaxing actions of the nariuretic peptides, and because genetically determined quantitative changes in the expression of this gene affect blood pressure and heart weight in a dose-dependent manner in mice. To determine whether there are common quantitative variants in human NPR1, we have sequenced the entire human NPR1 gene and identified 10 polymorphic sites in its non-coding sequence by using DNA from 34 unrelated human individuals. Five of the sites are single nucleotide polymorphisms; the remaining five are length polymorphisms, including a highly variable complex dinucleotide repeat in intron 19. There are three common haplotypes 5' to this dinucleotide repeat and three 3' to it, but the 5' haplotypes and 3' haplotypes appear to be randomly associated. Transient expression analysis in cultured cells of reporter plasmids with the proximal promoter sequences of NPR1 and its 3' untranslated regions showed that these polymorphisms have functional effects. We conclude that common NPR1 alleles can alter expression of the gene as much as two-fold and could therefore significantly affect genetic risks for essential hypertension and cardiac hypertrophy in humans.     

Structural and functional analysis of a growth-regulated gene, the human calcyclin

Calcyclin was originally defined as a cDNA clone (2A9) whose cognate RNA is growth-regulated and whose sequence shows strong similarities to the sequences of the S-100 protein, a calcium-binding protein, as well as to a subunit of the major cellular substrate for tyrosine kinase. Using the full-length cDNA, we have now isolated from a human genomic library several phages containing calcyclin sequences. One of the phages, ch. 28-10, contains the entire calcyclin gene, plus extensive flanking sequences. The calcyclin gene is a unique copy gene and has 3 exons. The 5' flanking sequence has been characterized, both structurally and functionally. Besides a TATA box, it contains, in the region proximate to the cap site, GC boxes and a sequence with a strong homology to the enhancer core of the SV40 promoter. Other enhancer-like elements are found scattered in both the 5' and 3' flanking regions. The proximate 5' flanking region is very active in driving the transient expression of linked reporters in transfection experiments. Finally, the calcyclin gene has been localized to the long arm of human chromosome 1, near the ski oncogene.     

Ancient repeated DNA elements and the regulation of the human frataxin promoter

Friedreich ataxia results from frataxin insufficiency caused by repeat expansion in intron 1 of the frataxin gene. Since the coding sequence is unchanged, the potential exists to ameliorate symptoms by increasing frataxin promoter activity. We therefore defined the minimal frataxin promoter in humans. Despite the fact that frataxin is an essential gene, its promoter is not well conserved in mammals, in part because it has been the frequent target of retroelement insertions. Most of the activity of the human frataxin promoter can be attributed to these retroelements, illustrating how these elements, considered parasitic by some, have been co-opted to drive critical genes. Individuals with the milder French Acadian form and those with the classic form of the disease have no biologically relevant sequence differences in the promoter or 3' UTR, suggesting that some other region of the gene, perhaps the repeat itself, is responsible for the difference in disease severity.