A chromosome integration system for stable gene transfer into Thermus flavus

We have developed a chromosomal integration system for gene transfer into the extreme thermophile Thermus flavus. The system relies on integration at the site of leuB (3-isopropylmalate dehydrogenase) which was cloned from T. flavus. The leuB gene was insertionally inactivated in vitro with a thermostable kanamycin-resistance gene and transformed in single-copy into the chromosome of T. flavus on a plasmid vector. Gene replacement strains required leucine for growth, were stably kanamycin-resistant and could grow in the presence of kanamycin at temperatures up to 55 degrees C.

IFN-gamma and lipopolysaccharide induce DNA binding of transcription factor PU.1 in murine tissue macrophages

The transcription factor PU.1, the Spi-1 oncogene product, is found principally in B cells and macrophages. PU.1 binds to a purine-rich sequence of DNA with a core consensus sequence of 5'-GAGGAA-3'. By using an electrophoretic mobility shift assay, we have been able to identify PU.1 in nuclear extracts of murine tissue macrophages. When macrophages are stimulated with IFN-gamma, an increase in PU.1 binding is observed. This increase is gradual, peaking at 6 to 9 h and decaying to basal levels 24 h after stimulation. The increase in PU.1 binding is unaffected by inhibiting protein synthesis, but is attenuated by either an inhibitor of the NA+/H+ antiporter or elevations in cAMP. In addition, we have found that low doses (1 ng/ml) of bacterial LPS induce PU.1 binding.

IFN-gamma and lipopolysaccharide induce DNA binding of transcription factor PU.1 in murine tissue macrophages

The transcription factor PU.1, the Spi-1 oncogene product, is found principally in B cells and macrophages. PU.1 binds to a purine-rich sequence of DNA with a core consensus sequence of 5'-GAGGAA-3'. By using an electrophoretic mobility shift assay, we have been able to identify PU.1 in nuclear extracts of murine tissue macrophages. When macrophages are stimulated with IFN-gamma, an increase in PU.1 binding is observed. This increase is gradual, peaking at 6 to 9 h and decaying to basal levels 24 h after stimulation. The increase in PU.1 binding is unaffected by inhibiting protein synthesis, but is attenuated by either an inhibitor of the NA+/H+ antiporter or elevations in cAMP. In addition, we have found that low doses (1 ng/ml) of bacterial LPS induce PU.1 binding.

The rRNA enhancer regulates rRNA transcription in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, the rRNA genes are organized as a tandem array of head-to-tail repeats. An enhancer of rRNA transcription is present just at the end of each transcription unit, 2 kb away from the next one. This enhancer is unusual for S. cerevisiae in that it acts both upstream and downstream of, and even across, genes. The role of the enhancer in the nutritional regulation of rRNA transcription was studied by introducing a centromere plasmid carrying two rRNA minigenes in tandem, flanking a single enhancer, into cells. Analysis of the transcripts from the two minigenes showed that the enhancer was absolutely required for the stimulation of transcription of rRNA that occurs when cells are shifted from a poor carbon source to a good carbon source. While full enhancer function is provided by a 45-bp region at the 3' end of the 190-bp enhancer, some activity was also conferred by other elements, including both a T-rich stretch and a region containing the binding sites for the proteins Reb1p and Abf1p. We conclude that the enhancer is composed of redundant elements and that it is a major element in the regulation of rRNA transcription.

A large-scale, short-term, media-based weight loss program

BACKGROUND

This article describes the evaluation of a media-based weight loss and nutrition program.

METHODS

Fifteen broadcasts were aired on a Chicago television news program over a three-week period in November of 1986. Some participants (n = 37) received the television program and an accompanying manual, and some (n = 37) received, in addition to the television and media interventions, encouragement to attend self-help groups dealing with obesity.

RESULTS

Repeated measures analysis of variance tests were performed, and planned comparisons were conducted only if main effects were significant. At posttesting, those participants attending the self-help groups lost an average of more than nine pounds, whereas those provided only the television program and manual had decreased by less than a pound. Those attending the groups had significantly decreased their percent of dietary fat intake, significantly increased aerobic exercise, and had significantly more hopefulness, motivation, and stimulus control.

DISCUSSION

The findings suggest that short-term mass media programs by themselves were probably not very effective, but when supplemented by a self-help manual and support groups may be able to produce significant short-term weight loss.

Termination of transcription of ribosomal RNA in Saccharomyces cerevisiae

We have attempted to determine the site of termination of transcription of ribosomal RNA in the yeast, Saccharomyces cerevisiae. While a quantitative description of the termination sites of RNA polymerase I is not possible using presently available methods, we conclude that transcription of most molecules continues through a large portion of the adjacent enhancer region. There are two potential termination sites within the enhancer, one of which is near the binding site of the DNA binding protein REBI. In addition there is an apparently fail-safe termination site approximately 950 nucleotides beyond the 3' end of 35S ribosomal precursor RNA. Processing at the end of 35S RNA influences the choice of downstream termination site. Conversely downstream sequences also influence the site of termination.

Activation of the cAMP cascade inhibits an early event involved in murine macrophage Ia expression

The ability of interferon-gamma (IFN gamma) to increase class II major histocompatibility complex (class II MHC) gene products in murine macrophages involves activation of Na+/H+ exchange (Prpic V., Yu, S. F., Figueiredo, F., Hollenbach, P. W., Gawdi, G., Herman, B., Uhing, R. J., and Adams, D. O. (1989) Science 244, 469-471). The ability of IFN gamma to increase class II MHC gene product expression is inhibited by a variety of agents. In the present studies, the involvement of cAMP-dependent protein kinase in modulating IFN gamma-induced expression of MHC gene products and the mechanism of regulation were assessed in macrophages treated with agents which activated cAMP-dependent protein kinase by different molecular mechanisms. Prostaglandin E2 (PGE2) produced a rapid (within 30 s) dose-dependent elevation of cAMP which was paralleled by the activation of cAMP-dependent protein kinase. The elevation of cAMP by PGE2 was still evident at 1 h and maintained through a 4-h incubation. Concentrations of PGE2 which activated the protein kinase produced a dose-dependent inhibition of surface expression of I-A and transcription of class II MHC genes. Inhibition of IFN gamma-induced class II MHC gene product expression was also observed in macrophages treated with agents which activated cAMP-dependent protein kinase by postreceptor mechanisms. Dibutyryl-cAMP (0.01-1 mM), 25 microM forskolin, 0.1 micrograms/ml cholera toxin, and 3-isobutyl-1-methylxanthine (0.1-1 mM) each suppressed IFN gamma-induced cell surface I-A expression, class II MHC gene transcription, and 22Na+ influx. The results are consistent with the suggestion that activation of cAMP-dependent protein kinase regulates an early transductional event initiated by IFN gamma, perhaps Na+/H+ exchange, which is involved in regulating transcription of class II MHC genes and their subsequent expression.

Unusual enhancer function in yeast rRNA transcription

The rRNA genes in most eucaryotic organisms are present in a tandem array. There is substantial evidence that transcription of one of these genes may not be independent of transcription of others. In particular, in the yeast Saccharomyces cerevisiae, the enhancer of rRNA transcription that lies 2.2 kilobases 5' of the transcription initiation site is at least partly within the upstream transcription unit. To ask more directly about the relationship of the tandemness of these genes to their transcription, we have constructed a minirepeat containing two identifiable test genes, with or without enhancer(s). On integration into the URA3 locus, these genes were transcribed by RNA polymerase I. A single enhancer effectively stimulated transcription of both genes by 10- to 30-fold, even when it was located upstream of both or downstream of both. Two enhancers had roughly additive effects. These results suggest a model of enhancer function in tandemly repeated genes.

Proteins that bind to the yeast rDNA enhancer

The transcription of ribosomal RNA genes differs from that of other genes in several respects: the use of a specialized polymerase, the generally high level of transcription, and the tandem arrangement of the genes. In the yeast Saccharomyces cerevisiae, we identified a nucleotide sequence in the "nontranscribed" spacer region that had many characteristics of an enhancer of transcription (8). More recently, it has become apparent that transcription of this sequence occurs (9) and that it may also be involved in some aspect of termination of 35 S rRNA transcription. The likelihood that there are protein factors involved in termination and activation of transcription and that these may participate in the coupling of the transcription of adjacent rRNA genes led us to search for proteins that might bind to the enhancer. We have identified two such proteins, termed REB1 and REB2, that bind to the enhancer and protect specific sequences from attack by chemical and enzymatic reagents. It is noteworthy that there is a second REB1 binding site approximately 210 base pairs upstream of the origin of transcription of rRNA and that binding of REB1 to this site alters the conformation of DNA adjacent to the site of initiation.

Phosphorylation of the Saccharomyces cerevisiae equivalent of ribosomal protein S6 has no detectable effect on growth

The phosphorylation of mammalian ribosomal protein S6 is affected by a variety of agents, including growth factors and tumor promoters, as well as by expressed oncogenes. Its potential role in the regulation of protein synthesis has been the object of much study. We have developed strains of Saccharomyces cerevisiae in which the phosphorylatable serines of the equivalent ribosomal protein (S10) were converted to alanines by site-directed mutagenesis. The S10 of such cells is not phosphorylated. Comparison of these cells with the parental cells, whose genomes differ by only six nucleotides, revealed no differences in the lag phase or logarithmic phase of a growth cycle, in growth on different carbon sources, in sporulation, or in sensitivity to heat shock. We conclude that in S. cerevisiae the phosphorylation of ribosomal protein S10 may play no role in regulating the synthesis of proteins. This conclusion leads one to ask whether certain protein phosphorylations are simply the adventitious, if easily observable, result of the imperfect specificity of one or another protein kinase.

Molecular inventory control in ribosome biosynthesis

The eukaryotic cell coordinates the accumulation of each ribosomal protein with every other ribosomal protein, with ribosomal RNA and with the needs of the cell. To do so it regulates the transcription, processing, translation and lifetime of the mRNA for ribosomal proteins. When all else fails, it rapidly degrades any excess ribosomal protein which is synthesized.

Phosphorylation of the yeast equivalent of ribosomal protein S6 is not essential for growth

The yeast equivalent of ribosomal protein S6, known as S10, can be modified by the addition of two phosphates. The two adjacent serines that are likely to be subject to phosphorylation were deduced by comparison with the known sites of phosphorylation on rat liver S6. Using oligonucleotide mutagenesis, we altered the gene for S10 to replace these two serines with alanines. This mutant gene was introduced into a diploid yeast cell heterozygous for each of the two S10 genes. After sporulation, we obtained colonies in which the mutant gene was the only intact S10 gene. Although the ribosomes of these cells contained a full complement of S10, no phosphorylation of S10 was detected. These cells grow exponentially with a doubling time about 50% greater than that of control cells. We conclude that the phosphorylation of S10 is not essential for growth. However, the mutant gene in such cells is very unstable, frequently reverting to wild type, presumably by interaction with the disrupted host genes. We suggest that at some stage of the growth cycle there is strong selection for S10 that can be phosphorylated.

Cyanogen bromide digestion of the avian myeloblastosis virus pp19 protein: isolation of an amino-terminal peptide that binds to viral RNA

The avian myeloblastosis virus pp19 protein was separated from the other virus proteins by a rapid and simple purification procedure which yields milligram amounts of homogeneous protein. This protein was then fragmented by digestion with cyanogen bromide. When the mixture of the cyanogen bromide peptides was passed through a 60S avian myeloblastosis virus RNA-cellulose column, only one peptide bound with high affinity to the resin. The peptide migrated on a sodium dodecyl sulfate-polyacrylamide gel with an approximate molecular weight of 2,900 and will be referred to as the p3B peptide. This peptide was also isolated directly by chromatography of the cyanogen bromide-digested pp19 protein on a reverse-phase high-pressure liquid chromatography column. It was again the only cyanogen bromide peptide of the pp19 protein that bound to the RNA affinity resin. The p3B peptide is a basic peptide, as was seen by its rapid migration on acid-urea-polyacrylamide gels and its amino acid composition. A partial amino acid sequence analysis of the p3B peptide indicated that it was derived from the amino terminus of the intact protein. Although the p3B peptide bound to 60S RNA, it did not demonstrate the selective binding of native pp19 to regions of the RNA containing secondary structure.

Myocardial renin-angiotensin extraction in man

Renin activity, renin substrate, and angiotensin II concentration were measured in the aortic and coronary sinus blood of 14 patients. There was a significant gradient for angiotensin II only. The gradient was diminished in areas of ischaemic myocardium. The study suggests that angiotensin II is partially bound, extracted, or destroyed in the coronary circulation of man.

Biochemical and morphological studies of rat submandibular gland: II. Partial purification of proteins from granule-rich fraction

Soluble proteins derived from a centrifuged and filtered granule-rich fraction of homogenized rat submandibular gland were analyzed by gel filtration, ion-exchange chromatography, and polyacrylamide gel electrophoresis. Both the granule-rich fraction and final supernatant fraction contained alkaline esterase activity. The major protein component, derived from granules of the convoluted tubules, was further resolved into a series of peptides ranging in molecular weight from 9,000 to 55,000 daltons.