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S Blume

Publications and source records attributed to S Blume.

14 recordsLinked to original sources
PubMed2001

SmtB-DNA and protein-protein interactions in the formation of the cyanobacterial metallothionein repression complex: Zn2+ does not dissociate the protein-DNA complex in vitro.

The synechococcal metallothionein locus smt consists of two divergent genes: smtA coding for the metallothionein SmtA, and smtB coding for the trans-acting regulator SmtB. The latter binds at two inverted repeats, designated S1/S2 and S3/S4, in the overlapping promoter/operator sites between the two genes. We have determined the binding stoichiometries to the entire operator/promoter DNA and to the separate S1/S2 and S3/S4 half-operator oligonucleotides using sedimentation equilibrium and sedimentation velocity measurements. The full promoter/operator DNA binds two SmtB dimers. The hydrodynamic behavior of this complex supports a compact nucleoprotein structure. Each separate S1/S2 and S3/S4 operator sequence also binds two dimers. An equal molar mixture of separate S1/S2 and S3/S4 operator sequences, in excess SmtB, forms a S1/S2-SmtB:SmtB-S3/S4 bridge complex. Combining these results with previously published binding interference data, which showed consecutive S1/S2 and S3/S4 SmtB occupancy on the operator/promoter DNA, we have developed a model for the establishment of the repression complex that appears to involve significant DNA compaction, presumably DNA bending, stabilized by SmtB-SmtB bridge interactions. DNase I footprinting titrations also showed consecutive S1/S2 and S3/S4 SmtB occupancy. The footprints expand considerably in the presence of Zn2+. Hence, SmtB remains bound to the operator sites when Zn2+ ions are present. This result is further supported by gel retardation assay. Failure of the metal ions to dissociate SmtB from the DNA points to a hitherto unknown function of SmtB in the regulation of the smt locus.

Amino Acid Sequence↗
PubMed2000

Technology assessment and the sociopolitics of health technologies.

In a growing number of countries, health technology assessment (HTA) has come to be seen as a vital component in policy making. Even though the assessment of the social, political, and ethical aspects of health technology is listed as one of its main objectives, in practice, the integration of such dimensions into HTA remains limited. Recent social scientific research on the inherently political nature of technology strongly supports such a comprehensive approach. The growing claims by and on behalf of consumer groups also suggest that HTA should be informed by a broader set of perspectives. Using the example of the cochlear implant in children, this essay compares the professed objectives of HTA with typical practice and explores possible explanations for the discrepancies observed. A second example, home telemonitoring for elderly persons, demonstrates how the types of evidence considered by HTA and the process through which assessments are produced may be reconsidered. We argue for the formal integration of the sociopolitical dimensions of health care technologies into assessments. The ability of HTA to more fully address important issues from a public policy point of view will increase by making explicit the sociopolitical nature of health care technologies.

Aged↗
PubMed1998

Molecular cDNA cloning and tissue distribution of mRNA encoding a novel ATP-binding cassette (ABC) half-transporter.

The majority of proteins belonging to the ATP-binding cassette (ABC) superfamily catalyzes translocation of substrates across biological membranes. Employing a reverse transcription-PCR approach with degenerate primers, we have identified a full-length cDNA from rat hepatocytes encoding a novel ABC transporter termed umat (ubiquitously expressed mammalian ABC half-transporter). The deduced sequence of 836 amino acids comprises an N-terminal membrane anchor domain and a single conserved C-terminal nucleotide binding fold, specifying umat as an ABC half-transporter. While the first 250 amino acid positions are highly divergent from other ABC transporters, clusters of conserved residues are evident along the rest of the protein. The greatest sequence similarity was observed with the fission yeast heavy metal tolerance protein hmt1 (44.5% identity in a 626-amino-acid overlap). Umat mRNA, expressed in all tissues analyzed, was most abundant in testis. Substantial umat mRNA expression in cultured primary rat hepatocytes suggests that hepatocyte cultures should represent an adequate model for investigation of umat function and regulation.

ATP-Binding Cassette Transporters↗
PubMed1992

Triplex formation prevents Sp1 binding to the dihydrofolate reductase promoter.

The human dihydrofolate reductase (DHFR) promoter sequence contains two consensus binding sites for the Sp1 regulatory protein. We have determined the effect of intermolecular triplex DNA formation on Sp1 binding to the DHFR promoter. The DHFR Sp1 binding site I (-39 to -48 relative to the DHFR transcription start site) demonstrates concentration-dependent triplex formation with a 19-base pair G-rich oligonucleotide (GR19) which is complementary to the polypyrimidine strand. DNase I footprint analysis demonstrates that GR19 forms a DNA triplex structure with the DHFR promoter fragment in a sequence-specific manner. DNase I footprinting analysis also indicates that the orientation of binding of these G-rich oligonucleotides is antiparallel. CR19, a C-rich complementary oligonucleotide, on the other hand, does not form triplex. The DNase I protection pattern of DHFR promoter fragment incubated with both recombinant Sp1 and triplex-forming oligonucleotide suggests that triplex formation prevents Sp1 binding. This is confirmed by gel shift analysis which demonstrates that triplex formation by the Sp1 binding sequences of the DHFR promoter prevents recombinant Sp1 binding in a concentration-dependent manner. These results demonstrate that intermolecular triplex formation prevents regulatory protein binding in a sequence-specific manner.

Base Sequence↗
PubMed1991

Mithramycin blocks transcriptional initiation of the c-myc P1 and P2 promoters.

The c-myc protooncogene plays an important role in the regulation of cellular proliferation. Mithramycin, a DNA binding antibiotic which binds G-C-rich DNA, inhibits c-myc expression in both differentiating and nondifferentiating cells. The G-C-rich nature of the c-myc promoter suggests that mithramycin may act by directly inhibiting promoter function. The mithramycin binding sites in the c-myc promoter regions were determined by DNAse I footprinting. Particularly prominent mithramycin binding is noted in the regions just 5' of the P1 and P2 promoter TATA boxes. Gel retardation experiments performed in the presence of mithramycin demonstrate that drug binding can prevent the formation of discrete complexes between HeLa cell nuclear proteins and c-myc promoter DNA fragments. Mithramycin also directly blocks the binding of the transcription factor Sp1 to the P1 promoter region. In vitro run-off transcription demonstrates that mithramycin can completely inhibit the in vitro function of both the P1 and P2 promoters. These data suggest that mithramycin inhibits transcription of the c-myc protooncogene by blocking the binding of important regulatory factors, thus preventing formation of the c-myc transcription initiation complex.

Base Sequence↗
PubMed1990

Oncogenes, malignant transformation, and modern medicine.

During the past decade there have been remarkable strides in the understanding of the basic mechanism of cancer. It is now clear that there is a set of genes, known as oncogenes, that can cause cells to become malignant if their expression is altered, either by mutation or overexpression. The products of these genes include growth factors, growth factor receptors, signal tranduction proteins, and DNA binding proteins. The normal cellular counterparts of these genes play very important roles in the regulation of growth and proliferation by normal cells. Another set of genes, anti-oncogenes, also play an important role in preventing abnormal cell proliferation. The remarkable explosion of understanding of the pathophysiology of malignancy has led to a common unifying concept of malignant transformation that applies to all tumors. It is likely that these new insights will lead to improved and more specific treatments for malignant disease in the next decade.

Animals↗
PubMed1983

Physicians in alcoholism: a study of current status and future needs.

Members of the American Medical Society on Alcoholism were studied to shed light on medical manpower needs in the alcoholism field. Findings were compared to AMA and federal survey data for all American physicians. AMSA respondents were broadly distributed among specialties: primarily psychiatrists, internists, and family practitioners. They were evenly divided between office-based and institutional practice, and most were on medical school faculties. Regarding alcoholism treatment, they generally agreed that Alcoholics Anonymous is necessary and that nonmedical counsellors are effective, although their attitudes on the etiology of alcoholism were divided. This sample of physicians in alcoholism, although not inclusive of all in the field, represents a diverse group, with differing clinical and educational needs.

Alcoholism↗