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A C Cato

Publications and source records attributed to A C Cato.

At least 73 records · Page 4Linked to original sources
PubMed1988

A 13 bp palindrome is a functional estrogen responsive element and interacts specifically with estrogen receptor.

Sequences located upstream of the transcription initiation site of the Xenopus vitellogenin A2 (vit A2) gene contain a hormone dependent enhancer that confers estrogen control to the heterologous thymidine kinase (tk) promoter. As a minimal functional estrogen responsive element (ERE), we have defined the 13 bp palindrome GGTCACAGTGACC. This ERE binds estrogen receptor preferentially in vitro. Although the ERE shares some structural features with the glucocorticoid responsive element (GRE) it is distinct from this element since it neither binds glucocorticoid receptor in vitro nor does it confer glucocorticoid inducibility to a fusion gene. Point mutations within the ERE decrease its affinity for the estrogen receptor and result in a complete loss of estrogen inducibility.

Animals↗
PubMed1988

DNA sequences outside the receptor-binding sites differently modulate the responsiveness of the mouse mammary tumour virus promoter to various steroid hormones.

Glucocorticoids, progestins and androgens all induce the transcription of the mouse mammary tumour virus (MMTV) DNA upon binding of their respective receptors to the hormone response element (HRE). This element is located between -202 and -59 5' upstream of the start of transcription on the MMTV long terminal repeat (LTR) region. The HRE contains four repeats of the hexanucleotide 5'-TGTTCT-3' to which the steroid hormone receptors are thought to bind. To investigate the contribution of the individual receptor-binding sites and neighbouring sequences to the steroid hormone action at the MMTV LTR promoter, we mutated various regions of the HRE and studied their response in transfection experiments. Each of the four receptor-binding sites was found to contribute substantially to the overall induction of transcription by all the various steroid hormones tested. This indicates that each individual receptor-binding site on the HRE is important for maximum hormone response. Additionally, we identified four separate sequences outside the receptor binding sites that differentially modulated the response of the MMTV LTR promoter to various steroids. One of these sequences binds the cellular factor, NFI. Thus the interaction of trans-acting factors with sequences outside the hormone receptor-binding sites controls the hormone response of the MMTV LTR promoter.

Acetyltransferases↗
PubMed1988

Mineralocorticoid regulation of transcription of transfected mouse mammary tumor virus DNA in cultured kidney cells.

Renal cells contain two corticosteroid-binding entities defined on the basis of hormone-binding selectivity as type I (mineralocorticoid) and type II (glucocorticoid). The mineralocorticoid, aldosterone can bind to both type I and type II receptors. This poses problems in defining the characteristics of a true mineralocorticoid regulated expression of specific genes. We have used chimaeric constructs bearing the mouse mammary tumor virus (MMTV) promoter to study aldosterone action in the feline renal cell line CRFK. We have shown that in these cells aldosterone induces MMTV transcription through its own receptor (type I). This induction of MMTV transcription by aldosterone is a primary response to the hormone. We have shown that the DNA sequences that mediate the aldosterone response overlap the hormone response element (HRE) required for the glucocorticoid, progestin, and androgen induction of transcription at the MMTV long terminal repeat region. Thus the aldosterone regulation of MMTV long terminal repeat transcription is identical to the mode of action of the other steroid hormones at this promoter.

Aldosterone↗
PubMed1988

Estrogen and progesterone receptor-binding sites on the chicken vitellogenin II gene: synergism of steroid hormone action.

The chicken vitellogenin II gene is transcriptionally activated by estrogens. In transient transfection experiments in human T47D cells that contain receptors for various steroids, we showed estradiol, progestin, and androgen responses of a chimeric chicken vitellogenin II construct. This construct consists of DNA sequences from -626 to -590 upstream of the start of transcription of the chicken vitellogenin gene linked to the herpes simplex virus thymidine kinase promoter driving the transcription of the bacterial chloramphenicol acetyltransferase gene. Treatment of the transfected T47D cells with a combination of estradiol and the progestin R5020 led to a superinduction of chloramphenicol acetyltransferase activity, showing a synergistic action of these two steroids. This synergism was not observed upon treatment of the transfected cells with estradiol and the androgen dihydrotestosterone. Using point mutations in the vitellogenin gene fragment, we showed in functional and in in vitro DNase I footprinting assays with a purified progesterone receptor that, for the synergistic action of estradiol and R5020 to occur, the progesterone receptor must be bound to the vitellogenin gene fragment. The progesterone receptor-binding site was localized at -610 to -590, close to the consensus sequence (-626 to -613) for estrogen receptor binding and function. We therefore demonstrate here that two different steroid hormones can be functionally synergistic through the interaction of their corresponding receptors with two different binding sites adjacent to one another.

Animals↗
PubMed1988

Progesterone induction of metallothionein-IIA gene expression.

Expression of the metallothionein gene is known to be induced by glucocorticoids in a variety of cells. Here we show that in human cell lines containing functional progesterone receptors, the endogenous metallothionein-IIA (hMTIIA) gene is inducible by the synthetic progestins R5020 and medroxy-progesterone acetate. That this effect reflects a direct interaction with the metallothionein gene is supported by our finding that the partially purified progesterone receptor binds to the promoter region of the gene in vitro. The limits of the DNase I footprint and the guanine residues protected in methylation studies with the progesterone receptor are similar to those previously described for the glucocorticoid receptor. Thus, the hormone regulatory element of the human metallothionein-IIA gene can mediate regulation by both glucocorticoids and progestins, as does the hormone regulatory element of mouse mammary tumor virus.

Animals↗
PubMed1987

Partial overlapping of binding sequences for steroid hormone receptors and DNaseI hypersensitive sites in the rabbit uteroglobin gene region.

Four DNaseI hypersensitive (HS) chromatin regions were found in the uteroglobin locus located at -3.7, -2.4, -0.1 and +4.1 kb with respect to the transcription start site of the gene. The three sites upstream of the gene are only detected in the hormonally stimulated endometrium and disappear after hormone withdrawal, whereas the site at +4.1 is also found in tissues that do not express uteroglobin. In the -2.4 HS region, which is strictly dependent on progesterone treatment, three DNaseI sites are clustered within a 240 bp DNA segment that contains 20 imperfect repeats of an octanucleotide motif. Upstream of the uteroglobin gene there are three regions containing binding sites for the glucocorticoid and the progesterone receptors, located at -3.7, -2.6/-2.7 and -2.4. The -2.4 region contains two binding sites for the hormone receptors flanking the central HS site. In footprinting experiments with naked DNA binding of the receptor also renders this site more susceptible towards digestion with DNaseI. The -2.6/-2.7 region contains three binding sites for the hormone receptors located 140 bp upstream of the HS -2.4. While the -3.7 HS is also located within a receptor binding fragment, there is no binding of the hormone receptors to the promoter region. Thus, interaction of the receptor with DNA sequences far upstream from the promoter alters the chromatin conformation of neighbouring sequences and results in transcriptional activation.

Animals↗
PubMed1987

The hormone response element of the mouse mammary tumour virus DNA mediates the progestin and androgen induction of transcription in the proviral long terminal repeat region.

Mouse mammary tumour virus (MMTV) gene expression has been shown to be regulated by glucocorticoids. A hormone response element (HRE) located between -202 and -59 upstream of the start of transcription in the long terminal repeat (LTR) region of the proviral DNA is required for this induction. We have investigated the role played by the HRE in the induction of MMTV LTR transcription by other classes of steroid hormones. Chimaeric constructs containing the HRE and the authentic LTR promoter linked to an indicator gene or the HRE linked to an otherwise hormone insensitive promoter directing the transcription of an indicator gene, were transfected into the human mammary tumour cell line T47D. Transcription at the MMTV LTR promoter or at the previously hormone-insensitive promoter was induced by progestins and androgens but not by oestradiol in transfected cells that contained functional receptors for these hormones. These results identify the HRE as the cis-acting element that mediates the progestin and androgen induction of MMTV LTR transcription. The HRE is therefore a DNA element that is required not just for glucocorticoid but also for progesterone and androgen induction of MMTV LTR transcription.

Acetyltransferases↗
PubMed1986

The hormone regulatory element of mouse mammary tumour virus mediates progesterone induction.

Sequences within the long terminal repeat region (LTR) of mouse mammary tumour virus (MMTV) confer progestin inducibility to either the tk-promoter or the MMTV-promoter in T47D cells, a human mammary tumour cell line which possesses high constitutive levels of progesterone receptor. In a clone of MCF7 cells, another human mammary tumour cell line with a low level of progesterone receptor, as well as in rat fibroblasts, glucocorticoid but not progestin induction is observed. The effect of the progesterone analogue R5020 is much more pronounced than the effect of dexamethasone, and at the concentrations required for maximal induction, R5020 does not significantly compete with binding of dexamethasone to the glucocorticoid receptor. In conjunction with previous results on the DNA binding of the glucocorticoid and progesterone receptors, these data show that two different steroid hormones, acting through their respective receptors, can mediate the induction of gene expression by interacting with the same DNA sequences. Our results suggest that the hormone regulatory element of MMTV may primarily be a progesterone-responsive element in mammary cells.

Breast Neoplasms↗
PubMed1986

Mechanism of gene regulation by steroid hormones.

A first understanding of the molecular events on the DNA level, underlying transcriptional regulation by steroid hormones, has been approached in the last 3 years by means of protein/DNA interaction studies, using purified receptors. This work summarizes our knowledge of how purified glucocorticoid and progestine receptors interact with their cognate regulatory elements associated with polymerase II dependent genes like mouse mammary tumour virus, the genes encoding human metallothionein IIA, chicken lysozyme, human growth hormone and rabbit uteroglobin. The resulting data agree with those of functional test systems, that have been gene-transfer experiments using stable transformants or transient expression. A consensus sequence for the regulatory element of the glucocorticoid receptor could be deduced that, in its three-dimensional representation, gives an impression of the steric mode of interaction. The regulatory elements of the progestine receptor overlap in two analysed cases with those of the glucocorticoid receptor, but are not identical. Furthermore, also a polymerase I transcribed gene encoding ribosomal RNA in the mouse could be shown to contain a glucocorticoid regulatory element that is functional in in vitro transcription experiments. Finally, the latest strategies are the cloning of the glucocorticoid receptor gene and the analysis of receptor-mediated topological effects.

Animals↗
PubMed1984

The nucleotide sequences recognized by the glucocorticoid receptor in the rabbit uteroglobin gene region are located far upstream from the initiation of transcription.

Although the expression of the uteroglobin gene in the lung is regulated by glucocorticoids, no binding sites for the glucocorticoid receptor are found in the promoter region nor can they be observed in the coding sequences. Instead a fragment situated 2.6 kb upstream from the start of transcription of the uteroglobin gene shows a high affinity for the receptor. Deoxyribonuclease I and methylation protection studies show three contiguous binding sites located within this fragment. All three sites show homology to the glucocorticoid receptor binding sites described for other genes. Two of them encompass the hexanucleotide 5'-TGTTCT-3', and the other binding site contains the homologue hexanucleotide, 5'-AGTCCT-3', but the contacts between the receptor and the hexanucleotides are equivalent to those found in other functional regulatory elements for glucocorticoids. These elements may therefore be responsible for the glucocorticoid regulation of uteroglobin gene expression by acting over a relatively long stretch of nucleotide sequences.

Animals↗
PubMed1983

The uteroglobin gene region: hormonal regulation, repetitive elements and complete nucleotide sequence of the gene.

Differential uteroglobin induction represents an appropriate model for the molecular analysis of the mechanism by which steroid hormones control gene expression in mammals. We have analyzed the structure and hormonal regulation of a 35 Kb region of genomic DNA in which the uteroglobin gene is located. The complete sequence of 3,700 nucleotides including the uteroglobin gene and its flanking regions has been determined, and the limits of the gene established by S1 nuclease mapping. Several regions containing repeated sequences were mapped by blot hybridization, one of which is located within the large intron in the uteroglobin gene. Analysis of the RNAs extracted from endometrium, lung and liver, after treatment with estrogen and/or progesterone shows that within the 35 Kb region, the uteroglobin gene is the only DNA segment whose transcription into stable RNA is induced by progesterone.

Amino Acid Sequence↗
PubMed1982

HeLa cell messenger RNAs of widely differing sizes encode certain heat shock proteins in the Mr region of 72 000-74 000.

Cloned cDNA sequences coding for specific 72 000-74 000 Mr HeLa cell heat shock proteins (HSPs) have been used as probes to examine cytoplasmic and nuclear RNA of heat shocked HeLa cells. The mRNAs for these HSPs vary widely in size. Whilst the beta-, delta- and epsilon-HSPs are encoded in mRNAs of 1.9 kb, the gamma-HSP arises from an mRNA three times that size. A search for putative nuclear precursors to these mRNAs revealed high Mr candidates at 15.8 kb which accumulate 1-2 h after the initial heat shock, thus supporting the notion that transcriptional control is important in the initial heat shock response.

Centrifugation, Density Gradient↗
PubMed1982

Hyperthermia and the heat-shock proteins of HeLa cells.

When HeLa cells are subject to hyperthermia, the synthesis of specific heat-shock proteins (HSP) is induced under a variety of thermal conditions. HSP synthesis does not occur at temperatures above 43 degrees C but requires return to a culture temperature of 37 degrees C. Maximal induction appears to be achieved if a brief hyperthermia treatment (10 min, 45 degrees -46 degrees C) is followed by 2 h "development" at 37 degrees C. The induction process requires transcription but not DNA replication, and general cell metabolism is probably also required, as induction does not occur if the heat-treated cells are returned to 4 degrees (rather than 37 degrees C) for development. A small proportion of the HSPs of 72-74 Kd are found in nuclei, but do not appear to bind to DNA. The bulk of these proteins, as well as those at 100 Kd, are cytoplasmic, but none are preferentially associated with mitochondria. Increased synthesis of the 100Kd and 72-74 Kd HSPs was also triggered by pretreatment of the cells with 5 x 10(-5) M sodium arsenite.

Amino Acids↗
PubMed1982

Isolation and structure of the gene for the progesterone-inducible protein uteroglobin.

Uteroglobin is a small steroid-binding protein that is differentially regulated by steroid hormones in several tissues of the rabbit. In endometrium, the levels of uteroglobin mRNA increase after progesterone administration due to an enhanced rate of transcription of the uteroglobin gene. As a prerequisite for understanding the molecular mechanisms that modulate uteroglobin gene expression, we have isolated and characterized the uteroglobin gene. We first synthesized, cloned, and sequenced a uteroglobin cDNA that was used to screen a rabbit gene library and to show that the uteroglobin gene is not reiterated in the rabbit genome. We obtained three recombinant phages containing uteroglobin gene sequences and covering 35 kilobases of the rabbit genome. The uteroglobin gene is 3 kilobases long and is composed of three short exons separated by a long and a short intron. The complete coding sequence, the short intron, part of the large intron, and the flanking sequences have been subjected to sequence analysis. The salient features of the nucleotide sequence, including the absence of a canonical "T-A-T-A box," are discussed. A possible relationship is considered between the exon-intron structure of the gene and the known structure and function of uteroglobin.

Amino Acid Sequence↗
PubMed1981

Polypeptides encoded by polyadenylated and non-polyadenylated messenger RNAs from normal and heat shocked HeLa cells.

There is an increased synthesis of proteins in the molecular weight region of 100,000 72,000-74,000 and 37,000 two hours after treatment of HeLa cells for 10 min at 45 degrees C. In vitro translation, using a rabbit reticulocyte cell-free protein synthesising system, of HeLa cell cytoplasmic RNA shows that the prominent 72,000-74,000 Mr heat shock protein band comprises seven polypeptide species (namely alpha d beta gamma delta epsilon zeta) and these polypeptides are directly encoded by both polyadenylated and nonpolyadenylated mRNA.

Animals↗
PubMed1981

Molecular cloning of cDNA sequences coding for the major (beta-, gamma-, delta- and epsilon-) heat-shock polypeptides of HeLa cells.

The method of differential in situ colony hybridisation and the technique of two-dimensional gel electrophoresis of polypeptides synthesized in vitro by mRNAs that hybridise specifically to recombinant plasmids bound to filter discs, have been used to isolate two cDNA HeLa heat-shock clones. Each of these two clones contains the plasmid pBR322 with a cDNA fragment of about 0.3 kb inserted into the PstI site. The two fragments hae different restriction maps. Whilst one of the recombinant plasmids, pHS2, contains a cDNA sequence that hybridises to mRNA coding for the HeLa heat-shock gamma-polypeptide, the other, pHS6, cross-hybridises with mRNAs that code for the HeLa heat-shock beta-, delta- and epsilon-polypeptides.

Base Sequence↗
PubMed1981

Isolation and fine structure organisation of an avian vitellogenin gene coding for the major estrogen-inducible mRNA.

Two phage lambda recombinant DNA clones covering the entire sequence of an avian vitellogenin gene, plus flanking regions, have been isolated from an erythrocyte DNA gene library and characterized by R-loop and restriction mapping. The total length of this avian vitellogenin gene is 23 kb. The cloned sequences flanking the gene at the 5' and 3' end are 7 and 3 kb, respectively. The total length of exons in the two clones is 6.7 kb (vitellogenin mRNA is 6.6 kb). The gene is interrupted by at least 25 introns with a mean intron length of 940 bp. Some 6--10 additional very small introns may also be present but they were not observed reproducibly. The mean exon length is 250 bp. Restriction endonuclease digests of total liver genomic DNA and lambda recombinant DNA were also analyzed by electrophoresis. Southern blotting and hybridization with cloned vitellogenin cDNA. The results show an identity of organisation of this vitellogenin in the DNA from the two sources, thus ruling out a possible cloning artifact. In contrast to Xenopus vitellogenin we have found no evidence to suggest that avian vitellogenin is encoded by a small family of related genes.

Animals↗