The novel exon, exon T, of the human progesterone receptor gene and the genomic organization of the gene

Recently, we have cloned the novel isoform of the progesterone receptor (PR) cDNA (PR isoform S cDNA) from the human testicular cDNA library. The isoform S cDNA consists of the novel exon (termed the exon S of the PR gene) and the exons 4-8 of the PR gene. In order to investigate the existence of the other isoform of the human PR cDNA, the human testicular cDNA library was screened by the exons 4-8 corresponding sequence of the human PR cDNA in the present study. As a result, we have identified a novel isoform of the PR cDNA (termed the PR isoform T cDNA (PR-T cDNA)), which consisted of a previously unidentified 5'-sequence and the exons 4-8 of the PR gene. The structure of this isoform T cDNA is essentially similar to that of the isoform S cDNA. By the genomic cloning, the 5'-sequence of the PR isoform T mRNA was demonstrated to originate from a novel independent exon, exon T, which was located in the 5'-upstream region of the exon S.     

Cloning of the novel isoform of the estrogen receptor beta cDNA (ERbeta isoform M cDNA) from the human testicular cDNA library

Our recent report has revealed the existence of the progesterone receptor (PR) isoform S, which consists of the novel PR exon S and exons 4-8 of the PR gene in the human testicular cDNA library. More recently, we have cloned the human estrogen receptor alpha (ERalpha) isoform S cDNA from the library. The ERalpha isoform S cDNA also contains the novel ERalpha exon S and exons 4-8 of the ERalpha cDNA. Based on these findings, we assumed that the novel isoform of cDNA like the PR- and ERalpha isoforms might exist in the human ER beta (ERbeta). In order to investigate this possibility, we have screened the human testicular cDNA library using the exons 4-8 corresponding sequence of the human ERbeta cDNA. Consequently, we have cloned a novel isoform of the ERbeta cDNA that consists of a previously unidentified 5'-sequence and the exons 5-8 of the ERbeta gene. We termed this isoform cDNA the "ERbeta isoform M cDNA". The 5'-sequence of the ERbeta isoform M cDNA was confirmed to be derived from a novel exon (termed the "exon M") by analysis of the genomic DNA. Moreover, we have analyzed the molecular size of the ERbeta isoform M encoded by the ERbeta isoform M mRNA by transient expression of the ERbeta isoform M cDNA in the 293T cell. The approximately 28 kDa protein, which was recognized by the anti-rat ERbeta antibody against the carboxyl-terminal region, was synthesized in the cells. Thus, we concluded that the ATG in the exon M could be used as the translation initiation codon. This report revealed for the first time the existence of the ERbeta mRNA isoform that is not caused by the skipping of one or more exons, by the alternative usage of the multiple exon 8s, nor by the alternative utilization of the untranslated 5'-exons located on the upstream region of the exon 1.     

Allelic genes involved in artery compliance and susceptibility to sporadic abdominal aortic aneurysm

Vascular smooth muscle cells (VSMCs) synthesize elastin (ELN), major protein of aortic tunica media which confers strength and elasticity to aortic wall. Protein loss or distortion is typical in aneurysm tunica media. Transforming growth factor β1 (TGFβ1) inhibits growth and connective protein expression of abdominal VSMCs cultures. Also, in atherogenic studies, estrogen (but not estrogen plus progestin) treatments inhibit aortic collagen accumulation and elastic loss, risk factors to subsequent aortic enlargement. Therefore, polymorphisms of ELN, estrogen receptor (ER) and β (ERβ), progesterone receptor (PR) and TGFβ1 genes and their products may be involved in the abdominal aortic aneurysm (AAA) development. Using PCR-RFLP method, we analyzed ELN RmaI (exon 16), ER PvuII-XbaI (intron 1), ERβ AluI (exon 8), PR TaqI (intron 7) and TGFβ1 Bsu36I (−509 bp, promoter) polymorphisms in 324 Caucasian male subjects: 225 healthy controls (mean age 71.20 ± 6.85 years) and 99 unrelated AAA patients (mean age 69.8 ± 7.1 years). No difference in ELN, ER, PR and TGFβ1 allele frequencies was observed in AAA patients versus controls (P > 0.05). However, because possessing at least an ERβ AluI restriction site was statistically associated to AAA onset (χ² = 5.220; OR = 1.82, P < 0.05), ERβ polymorphism was proposed as genetic determinant in the AAA susceptibility.     

The multiple untranslated first exons and promoters system of the oestrogen receptor gene in the brain and peripheral tissues of the rat and monkey and the developing rat cerebral cortex

Recent studies on the human oestrogen receptor (ER) gene have revealed the complex system with the multiple untranslated first exons and promoters in the ER gene expression. Little information is however available on the system in the ER gene of the rat or nonhuman primate. The rat genomic library was first screened by the rat ER cDNA (0–1) probe. One of the four positive clones (λ rEgEl) was subcloned and sequenced. The nucleotide sequence was found to contain the exon 0, the intron 0, and the exon 1 with its 3′-ends. The novel untranslated first exons, the exon ON and the exon OS, were further identified. These results indicated the presence of at least four subtypes of the rat ER mRNAs; the messages transcribed from promoter P-0 (ER mRNA (0–1)), putative promoter P-1 (ER mRNA (1–1)), promoter P-ON (ER mRNA (ON-1)) and promoter P-OS (ER mRNA (OS-1)). The P-O- or P-1 driven message (0–1) or (1–1) appeared to be expressed most strongly in major oestrogen central- (anterior pituitary, AP, hypothalamus–preoptic area, HPOA, and amygdala, AMG) and peripheral targets (uterus and ovary). The message (ON-1) was strongly expressed in the liver and kidney, but not in the HPOA, AMG, cerebral cortex, CC, and cerebellum, Ce. The OS-1 message was expressed variably but generally in the tissues examined except for the CC and Ce. Thus, the region- and tissue specific expression of the rat ER gene is likely to be regulated by the multiple untranslated exons and promoters system. Furthermore, when the ER mRNA subtypes were examined in the rat neonatal CC where the ER protein level rose transiently, considered as a model for the development of the ER or progestin receptor A and B isoforms, the expression of the ER mRNAs seemed to be differential postnatally, implicating some stage dependent usage of the promoters in the development. In the monkey, we identified the untranslated first exon OS, the homologue of the rat exon OS. Interestingly, the exon C was found to consist of two different exons, the exon OK and the exon OG. By the alternative usage of the promoters and the alternative splicing, at least six ER mRNA subtypes, that is, ER mRNAs (0–1), (1–1), (OS-1), (OS-OG-1), (OK-1) and (OK-OG-1) were identified in the monkey tissues. These messages were also differentially distributed in the monkey brain and other tissues. It was noteworthy that the P-OK driven messages were expressed almost exclusively in the monkey liver. These results have suggested that the systems of the multiple untranslated first exons and promoters and the alternative splicing are involved in the regulation of the region- and tissue specific expression of the ER gene in the brain and peripheral tissues of the rat and monkey. Stage-related usage of the promoters was also suggested in the ER gene expression in the CC of the postnatal rat in development.     

Estrogen Stimulates Degradation of ��-Amyloid Peptide by Up-regulating Neprilysin

Postmenopausal estrogen depletion is a characterized risk factor for Alzheimer disease (AD), a human disorder linked to high levels of β-amyloid peptide (Aβ) in brain tissue. Previous studies suggest that estrogen negatively regulates the level of Aβ in the brain, but the molecular mechanism is unknown. Here, we provide evidence that estrogen promotes Aβ degradation mainly through a principal Aβ degrading enzyme, neprilysin, in neuroblastoma SH-SY5Y cells. We also demonstrate that up-regulation of neprilysin by estrogen is dependent on both estrogen receptor α and β (ERα and ERβ), and ligand-activated ER regulates expression of neprilysin through physical interactions between ER and estrogen response elements (EREs) identified in the neprilysin gene. These results were confirmed by in vitro gel shift and in vivo chromatin immunoprecipitation analyses, which demonstrate specific binding of ERα and ERβ to two putative EREs in the neprilysin gene. The EREs also enhance ERα- and ERβ-dependent reporter gene expression in a yeast model system. Therefore, the study described here provides a putative mechanism by which estrogen positively regulates expression of neprilysin to promote degradation of Aβ, reducing risk for AD. These results may lead to novel approaches to prevent or treat AD.     

Activation of estrogen receptor-beta by a special extract of Rheum rhaponticum (ERr 731), its aglycones and structurally related compounds

The special extract ERr 731^® from the roots of Rheum rhaponticum is the major constituent of Phytoestrol^® N which is used for the treatment of climacteric symptoms in menopausal women. However, the molecular mode of action of ERr 731^® was unknown. For the first time, ERr 731^® and its aglycones trans-rhapontigenin and desoxyrhapontigenin were investigated with regard to the activation of the estrogen receptor- or estrogen receptor-β (ER, ERβ). The related hydroxystilbenes cis-rhapontigenin, resveratrol and piceatannol were studied as comparators. As controls, 17β-estradiol or the selective ER-(propylpyrazoltriol) or ERβ-agonists (diarylpropionitril) were used. Neither in ER-expressing yeast cells, in the ER-responsive Ishikawa cells, nor in human endometrial HEC-1B cells transiently transfected with the ER an activation of ER by ERr 731^® or the other single compounds was detected. Furthermore, an antiestrogenic effect was not observed. In contrast in human endometrial HEC-1B cells transiently transfected with the ERβ, 100 ng/ml ERr 731^® and the single compounds significantly induced the ERβ-coupled luciferase activity in a range comparable to 10⁻⁸ M 17β-estradiol. All effects were abolished with the pure ER antagonist ICI 182780, indicating an ER-specific effect. The ERβ agonistic activity by ERr 731^® could be of importance for its clinical use, as central functions relevant to climacteric complaints are proposed to be mediated via ERβ activation.