Promoter elements of genes coding for proteins and modulation of transcription by estrogens and progesterone.
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Biomedical subjects
Publications and source records attributed to A Krust.
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cDNA clones corresponding to a mRNA whose level is rapidly increased by addition of oestradiol to the culture medium have been isolated by differential screening of a cDNA library from the breast cancer cell line MCF-7, which contains oestrogen receptors. Such clones will be useful in studies of the DNA sequences required for hormonal induction and to determine whether expression of the corresponding gene is in any way related to the cancerous state. We have also obtained a cDNA clone for a messenger whose level is apparently decreased by steroid hormones.
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Three alpha-type globin genes have been identified in the alpha-globin linkage group of chickens. No other alpha-type genes hae been directly shown to be within 10 kilobase pairs of any of these three closely linked genes. These three genes have been conclusively identified by DNA sequence analysis. The gene at the 5' end of the linkage group is an embryonic alpha-type globin gene, pi or pi', and the central gene corresponds to the minor adult alpha- globin, alpha D. The 3'-terminal gene sequence corresponds to the sequence of cDNA clones previously described as "alpha S", presumed anemic shock-induced alpha-globin gene [Salser, W. A., Cummings, I., Liu, A., Strommer, J., Padayatty, J. & Clarke, P. (1979) in Cellular and Molecular Regulation of Hemoglobin Switching, eds. Stamatoyannopoulos, G. & Nienheis, A. (Grune and Stratton, New York), pp. 621-643; Richards, R. I. & Wells, J. R. E. (1980) J. Biol. Chem. 255, 9306-9311]. Several groups of workers have isolated alpha S-type cDNA clones but no one has identified a cDNA clone corresponding to the published amino acid sequence of the major chicken alpha-globin, alpha A. We have identified the alpha S-type sequence as the only abundant alpha-like globin sequence in cDNA clones made from reticulocyte mRNA isolated from nonanemic chickens. Therefore, we suggest that the alpha S-type sequence corresponds to the true alpha A-globin species.
A comparison of the organization of six avian adult globin messenger sequences is based on previously reported recombinant duck adult globin cDNA plasmids (Therwath et al., 1980) and the actual construction and characterization of pBR322 recombinant plasmids including the beta and the normal alpha A and alpha D chicken adult globin mRNA sequences. Identification of the cloned DNA was performed using hybridization-selection under conditions permitting complete purification in one step of the three globin mRNAs, and translation of the corresponding mRNA. Orientation of the globin insert in the vector was determined, taking into account the computer prediction of the restriction sites based on the known amino acid sequences of the three globin chains (Roizès and Pelaquier, 1980) and those actually observed, and by identification of restriction fragments using 3'-specific probes. Identification, orientation and restriction mapping of these cloned DNAs reveals extensive homologies in organisation of beta sequences between duck and chicken, as well as among the alpha sequences in every two possible combinations.
The lysozyme gene has been purified by molecular cloning from two chicken gene libraries. Several recombinant phages harbouring sequences homologous to a plasmid carrying a double stranded lysozyme cDNA have been isolated. One recombinant appears to carry an entire lysozyme gene. Electron microscopic studies show that the latter is split by at least three introns. The length of the gene is about 3.9 kb, 6 times longer than lysozyme mRNA.
Chicken conalbumin double-stranded cDNA (con-dscDNA) was synthesized from a laying hen oviduct mRNA preparation enriched for conalbumin mRNA (con-mRNA). The dscDNA was inserted by blunt-end ligation into the Sal I site of plasmid pBR322 which had been repaired with DNA polymerase I to create Taq I sites on each side of the inserted fragment. After bacterial transformation, one hybrid recombinant, pBR322-con1, which contains the largest inserted dscDNA (about 2350 bp) was shown to hybridize specifically to the RNA which is translated into conalbumin. Electron microscopic examination of hybrid molecules between con-mRNA and pBR322-con1 DNA indicate that the inserted con-dscDNA is an almost full-length double-stranded transcript of conalbumin mRNA.
A cloned DNA transcript of ovalbumin mRNA was cut a few nucleotides away from the initiator codon, and fused in phase to the beginning of the Escherichia coli beta-galactosidase gene. The hybrid gene has been cloned in E. coli where it produces large amounts of an ovalbumin-like protein.
An EcoRI fragment of chicken DNA (fragment 'a') containing a sequence complementary to the 3' half of ovalbumin mRNA has been isolated by molecular cloning. Analysis of the cloned fragment proves conclusively that the chicken ovalbumin gene is split. Fragment 'a' contains no extensive sequence repeated elsewhere in the genome and represents the only type of organisation of this part of the split ovalbumin gene in chicken genome.
The Eco RI fragments "c" and "d" of the ovalbumin gene (1, 2) have been isolated by molecular cloning. Restriction enzyme mapping and electron microscopy have confirmed that the two fragments contain the same ovalbumin mRNA coding sequences. These sequences are split into two regions which have been mapped in fragments "c" and "d". There is no evidence that the ovalbumin mRNA sequences contained in these fragments could be further interrupted. Our results confirm that the presence of Eco RI fragment "d" in some chickens is due to the existence of an allelic variant of the ovalbumin gene which contains an additional Eco RI site within the region corresponding to Eco RI fragment "c". This additional Eco RI site appears to be the main difference between the two alleles. Finally, our results provide a direct demonstration that most of the ovalbumin mRNA sequences are encoded for by Eco RI fragments "a", "b" and "c".
Double-stranded DNA molecules complementary to ovalbumin chicken messenger RNA were synthesized in vitro and integrated into the E. coli plasmid pCR1 using an oligodG-dc tailing procedure. The resultant hybrid plasmids, amplified by transfection of E. coli, were shown by hybridization and gel electrophoresis to contain extensive DNA sequences of the ovalbumin structural gene.
We have cloned and sequenced the complete complementary DNA of the oestrogen receptor (ER) present in the breast cancer cell line MCF-7. The expression of the ER cDNA in HeLa cells produces a protein that has the same relative molecular mass and binds oestradiol with the same affinity as the MCF-7 ER. There is extensive homology between the ER and the erb-A protein of the oncogenic avian erythroblastosis virus.
A cDNA encoding a protein that binds retinoic acid with high affinity has been cloned. The protein is homologous to the receptors for steroid hormones, thyroid hormones and vitamin D3, and appears to be a retinoic acid-inducible trans-acting enhancer factor, suggesting that the molecular mechanisms of the effect of retinoids (vitamin A) on embryonic development, differentiation and tumour cell growth are similar to those described for other members of this nuclear receptor family.