Biomedical subjects

M Truss

Publications and source records attributed to M Truss.

45 records · Page 3Linked to original sources

PubMed1992

Transcriptional control by steroid hormones.

Gene regulation by steroid hormones leads to induction or repression of particular sets of genes. These effects are mediated by intracellular hormone receptors that, in the unliganded state, are maintained in an inactive form by unknown mechanisms possibly involving association with other cellular proteins. Induction of the mouse mammary tumor virus (MMTV) requires binding of the hormone receptor to a complex hormone-responsive element (HRE) located between 75 and 190 bp upstream from the start of transcription. The interaction of several receptor molecules with the four receptor binding sites in the HRE is highly cooperative on circular DNA molecules and each individual site is needed for optimal induction. In chromatin the HRE is precisely organized in phased nucleosomes. Following hormone treatment and receptor binding, changes in chromatin structure are detected that correlate with binding of transcription factors, including nuclear factor I, to the MMTV promoter. However, though nuclear factor I acts as a basal transcription factor on the MMTV promoter it does not cooperate with the hormone receptors in terms of binding to free DNA, and mutation of the nuclear factor I binding site does not eliminate hormonal stimulation. This residual induction is mediated by octamer motifs, upstream of the TATA box, that bind the ubiquitous transcription factor OTF-1. Mutation of these octamer motifs does not influence basal transcription in vitro, but completely abolishes the stimulatory effect of progesterone receptor.

Amino Acid Sequence↗

PubMed1992

[ESWL in hemophilia B].

One of the most dramatic dangers in treating nephrolithiasis by ESWL is the development of intra- and perirenal bleeding, which requires therapeutic intervention. Even in patients whose blood parameters suggest they are healthy, hematomas are found in up to 80%. Therefore, ESWL must be regarded as contraindicated in patients with blood disorders. A case of a patient suffering from hemophilia B and from a large renal pelvic stone is reported, whom we treated by ESWL twice after sufficient substitution. X-ray revealed that the patient was stone-free on the 25th day after the first ESWL session. ESWL. A review of the literature is presented.

Adult↗

PubMed1991

Functional interaction of hybrid response elements with wild-type and mutant steroid hormone receptors.

Steroid hormone receptors can be divided into two subfamilies according to the structure of their DNA binding domains and the nucleotide sequences which they recognize. The glucocorticoid receptor and the progesterone receptor (PR) recognize an imperfect palindrome (glucocorticoid responsive element/progesterone responsive element [GRE/PRE]) with the conserved half-sequence TGTYCY, whereas the estrogen receptor (ER) recognizes a palindrome (estrogen responsive element) with the half-sequence TGACC. A series of symmetric and asymmetric variants of these hormone responsive elements (HREs) have been tested for receptor binding and for the ability to mediate induction in vivo. High-resolution analysis demonstrates that the overall number and distribution of contacts with the N-7 position of guanines and with the phosphate backbone of various HREs are quite similar for PR and ER. However, PR and glucocorticoid receptor, but not ER, are able to contact the 5'-methyl group of thymines found in position 3 of HREs, as shown by potassium permanganate interference. The ER mutant HE84, which contains a single amino acid exchange, Glu-203 to Gly, in the knuckle of ER, creates a promiscuous ER that is able to bind to GRE/PREs by contacting this thymine. Elements with the sequence GGTCAcagTGTYCT that represent hybrids between an estrogen response element and a GRE/PRE respond to estrogens, glucocorticoids, and progestins in vivo and bind all three wild-type receptors in vitro. These hybrid HREs could serve to confer promiscuous gene regulation.

Animals↗

PubMed1990

Structural features of a regulatory nucleosome.

DNA sequences from the long terminal repeat of the mouse mammary tumor virus (MMTV-LTR) position nucleosomes both in vivo and in vitro. Here, were present chromatin reconstitution experiments showing that MMTV-LTR sequences from -236 to +204 accommodate two histone octamers in positions compatible with the in vivo data. This positioning is not influenced by the length of the DNA fragment and occurs in linear as well as in closed circular DNA molecules. MMTV-LTR DNA sequences show an intrinsic bendability that closely resembles its wrapping around the histone octamer. We propose that bendability is responsible for the observed rotational nucleosome positioning. Translational nucleosome positioning seems also to be determined by the DNA sequence. These data, along with the results from reconstitution experiments with insertion mutants, support a modular model of nucleosome phasing on MMTV-LTR, where the actual positioning of the histone octamer results from the additive effect of multiple features of the DNA sequence.

Base Sequence↗

PubMed1990

DNA rotational positioning in a regulatory nucleosome is determined by base sequence. An algorithm to model the preferred superhelix.

MMTV-LTR sequences -190/-45 position a histone octamer both in vivo and in vitro. Experimental evidence suggested that nucleosome rotational positioning is determined by the DNA sequence itself. We developed an algorithm that is able to predict the most favorable path of a given DNA sequence over a histone octamer, based on rotational preferences of different dinucleotides. Our analysis shows that these preferences are sufficient for explaining the observed rotational positioning of the MMTV-LTR nucleosome, at one base pair accuracy level. Computer-generated 3-D models of the experimentally calculated and predicted MMTV-LTR nucleosome show that the predicted orientation is fully compatible with the currently available data in terms of accessibility of relevant sequences to regulatory proteins.

Algorithms↗

PubMed1990

Contacts between steroid hormone receptors and thymines in DNA: an interference method.

Understanding the mechanisms by which regulatory proteins recognize genetic information stored in DNA relies on the availability of methods to analyze their interaction with individual nucleotides and their reactive groups. Here we describe the use of KMnO4 to analyze the contacts between steroid hormone receptors and thymines within a hormone responsive element. Although several pyrimidine residues are highly conserved among different receptor binding sites their participation in sequence recognition has not been directly studied. Using an interference procedure based on selective modification of the thymine ring by KMnO4, we detect intimate contacts between the glucocorticoid or progesterone receptors and three thymine residues within the promoter distal receptor binding site of the mouse mammary tumor virus (-190/-160). A comparison of binding data obtained with oligonucleotides containing desoxyuridine, bromodeoxyuridine, cytosine, or 5'-methylcytosine instead of thymines demonstrates that the methyl group of those three thymines contributes to the free energy of binding. This simple method could be of general utility for the study of sequence-specific protein-DNA interactions.

Animals↗

PubMed1988

Relatedness of archaebacterial RNA polymerase core subunits to their eubacterial and eukaryotic equivalents.

The sequence of the genes encoding the four largest subunits of the RNA polymerase of the archaebacterium Methanobacterium thermoautotrophicum was determined and putative translation signals were identified. The genes are more strongly homologous to eukaryotic than to eubacterial RNA polymerase genes. Analysis of the polypeptide sequences revealed colinearity of two pairs of adjacent archaebacterial genes encoding the B" and B' or A and C genes, respectively, with two eubacterial and two eukaryotic genes each encoding the two largest RNA polymerase subunits. This difference in sequence organization is discussed in terms of gene fusion in the course of evolution. The degree of conservation is much higher between the archaebacterial and the eukaryotic polypeptides than between the archaebacterial and the eubacterial enzyme. Putative functional domains were identified in two of the subunits of the archaebacterial enzyme.

Amino Acid Sequence↗

PubMed1988

Cloning and physical mapping of RNA polymerase genes from Methanobacterium thermoautotrophicum and comparison of homologies and gene orders with those of RNA polymerase genes from other methanogenic archaebacteria.

The structural genes encoding the four largest subunits of RNA polymerase, A, B', B", and C, were physically mapped in Methanobacterium thermoautotrophicum Winter. The genes formed a cluster in the order B", B', A, C and had a common orientation. DNA hybridization experiments yielded different degrees of homology between RNA polymerase gene sequences of different species of Methanobacterium and Methanococcus voltae. No homology was detectable between Methanobacterium thermoautotrophicum and Methanosarcina barkeri. From Southern hybridization experiments in which probes of the four genes from Methanobacterium thermoautotrophicum Winter and restriction digests of the genomic DNAs of the different methanogens were used, a common gene order of the RNA polymerase genes could be deduced.

Archaea↗

PubMed1987

High resolution scanning of absorbing and fluorescent electrophoresis gels using video image analysis.

A low cost, microcomputer-controlled image analysis system is described which scans electrophoresis gels or photographic negatives with high resolution. Absorbing gels (e.g. with stained proteins) are analyzed using broadband or monochromatic visible light. The gel is scanned by a video camera with a macro objective; the gray level of each pixel is digitized sequentially and the values are stored in the computer memory. Repetitive scanning is used to average the absorption values before plotting on a digital plotter. Photographic negatives of gels and autoradiograms are scanned using the same technique. Fluorescent, non-absorbing gels (e.g. nucleic acids stained with ethidium bromide) are analyzed on a transilluminator with u.v. excitation radiation. The fluorescence intensity of each pixel is digitized and processed as described above.

Autoradiography↗