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S I Reed

Publications and source records attributed to S I Reed.

At least 145 records · Page 8Linked to original sources
PubMed1986

Sequence analysis of temperature-sensitive mutations in the Saccharomyces cerevisiae gene CDC28.

Eleven independently isolated temperature-sensitive mutations in the cell division cycle gene CDC28 were mapped with respect to the DNA sequence of the wild-type gene and then sequenced to determine the precise nature of each mutation. The set yielded six different point mutations, each of which predicts a single amino acid substitution in the CDC28 product. The positions of the mutations did not correlate in any obvious way with observable biological characteristics of the mutant alleles. When the positions of substitutions were collated with a predicted secondary structural analysis of the CDC28 protein kinase, they were found to correlate strongly with probable regions of structural transition.

Amino Acid Sequence↗
PubMed1985

Protein kinase activity associated with the product of the yeast cell division cycle gene CDC28.

Antibodies raised against the protein encoded by a lacZ-CDC28 in-frame fusion were shown to immunoprecipitate the CDC28 product from yeast cell lysates. The polypeptide p36CDC28 is a phosphoprotein of apparent Mr 36,000. Immune complexes prepared from yeast cell lysates by using anti-CDC28 antibody were found to possess a protein kinase activity, as determined by the transfer of label from [gamma-32P]ATP to a coprecipitated Mr 40,000 protein of unknown identity or function (p40). This activity was absent or thermolabile when extracts were prepared from several different cdc28 temperature-sensitive strains. The protein kinase activity was dependent on Zn2+ and transferred phosphate specifically to serine and threonine residues.

Amino Acid Sequence↗
PubMed1985

Regulation of CDC9, the Saccharomyces cerevisiae gene that encodes DNA ligase.

We have cloned CDC9, the structural gene for Saccharomyces cerevisiae DNA ligase, and investigated its transcriptional regulation both as a function of cell cycle stage and after UV irradiation. The steady-state level of DNA ligase mRNA increases at least fourfold in late G1, after the completion of start but before S phase. This high level of CDC9 mRNA then decays with an apparent half-life of ca. 20 min and remains at a low basal level throughout the rest of the cell cycle. The accumulation of CDC9 mRNA in late G1 is dependent upon the completion of start but not the CDC7 and CDC8 functions. Exposure of cells to UV light elicits an eightfold increase in DNA ligase mRNA levels.

Cell Cycle↗
PubMed1983

Isolation and transcriptional characterization of three genes which function at start, the controlling event of the Saccharomyces cerevisiae cell division cycle: CDC36, CDC37, and CDC39.

The genes CDC36, CDC37, and CDC39, thought to function in the cell division control process in Saccharomyces cerevisiae, were isolated from a recombinant plasmid library prepared by partial digestion of S. cerevisiae genomic DNA with Sau3A and insertion into the S. cerevisiae-Escherichia coli shuttle vector YRp7. In each case, S. cerevisiae DNA sequences were identified which could complement mutant alleles of the gene in question and which could direct integration of a plasmid at the chromosomal location known to correspond to that gene. Complementing DNA segments were subcloned to remove extraneous coding regions. The coding regions corresponding to CDC36, CDC37, and CDC39 were then identified and localized by R-loop analysis. The estimated sizes of the three coding regions were 615, 1,400, and 2,700 base pairs, respectively. Transcriptional orientation of the coding regions was established by using M13 vectors to prepare strand-specific probes followed by hybridization to blots of electrophoresed S. cerevisiae mRNA. The intracellular steady-state abundance of the mRNA species corresponding to the genes was estimated by comparing hybridization signals on RNA blots to that of a previously determined standard, the cell cycle start gene CDC28. The quantities calculated for the three mRNA species were low, ranging from 1.5 +/- 1 copies per haploid cell for the CDC36 mRNA to 3.1 +/- 1.5 and 4.6 +/- 2 copies per haploid cell for the CDC37 and CDC39 mRNAs, respectively. The CDC28 mRNA had been previously estimated at 7.0 +/- 2 copies per cell.

Cell Cycle↗
PubMed1982

Preparation of product-specific antisera by gene fusion: antibodies specific for the product of the yeast cell-division-cycle gene CDC28.

Antisera with specificity for the product of a yeast cell-division-cycle (CDC) gene were prepared by immunizing rabbits to a novel hybrid polypeptide. A segment of the yeast gene CDC28 was fused to the Escherichia coli lacZ gene, which encodes beta-galactosidase, by insertion of yeast sequences into the plasmid pBGF1. pBGF1 contains the lac promoter-operator and most of the lacZ gene. An EcoRI site, 16 codons upstream from the carboxyterminus of the beta-galactosidase coding region, served as a convenient splicing site for the heterologous sequences. To insure that an open reading frame be maintained between the two gene segments for some portion of the fusions, the CDC28-encoding segments were first subjected to limited digestion with nuclease BAL31 to produce random junction points. A hybrid polypeptide encoded by such a continuous open reading frame was purified from E. coli by preparative SDS-polyacrylamide gel electrophoresis and used to immunize rabbits. The resulting antisera were shown to have specificity for CDC28 gene product synthesized by cell-free translation of yeast mRNA.

Antibodies↗
PubMed1982

Preliminary characterization of the transcriptional and translational products of the Saccharomyces cerevisiae cell division cycle gene CDC28.

The CDC28 gene was subcloned from a plasmid containing a 6.5-kilobase-pair segment of Saccharomyces cerevisiae DNA YRp7(CDC28-3) by partial digestion with Sau3A and insertion of the resulting fragments into the BamHI sites of YRp7 and pRC1. Recombinant plasmids were obtained containing inserts of 4.4 and 3.1 kilobase pairs which were capable of complementing a cdc28(ts) mutation. R-loop analysis indicated that each yeast insert contained two RNA coding regions of about 0.8 and 1.0 kilobase pairs, respectively. In vitro mutagenesis experiments suggested that the smaller coding region corresponded to the CDC28 gene. When cellular polyadenylic acid-containing RNA, separated by agarose gel electrophoresis after denaturation with glyoxal and transferred to nitrocellulose membrane, was reacted with labeled DNA from the smaller coding region, and RNA species of about 1 kilobase in length was detected. Presumably, the discrepancy in size between the R-loop and electrophoretic determinations is due to a segment of polyadenylic acid which is excluded from the R-loops. By using hybridization of the histone H2B mRNAs to an appropriate probe as a previously determined standards, it was possible to estimate the number of CDC28 mRNA copies per haploid cell as between 6 and 12 molecules. Hybrid release translation performed on the CDC29 mRNA directed the synthesis of a polypeptide of 27,000 daltons, as determined by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. This polypeptide was not synthesized when mRNA prepared from a cdc28 nonsense mutant was translated in a parallel fashion. However, if the RNA from a cell containing the CDC28 gene on a plasmid maintained at a high copy number was translated, the amount of in vitro product was amplified fivefold.

Base Sequence↗
PubMed1981

Construction and characterization of three yeast-Escherichia coli shuttle vectors designed for rapid subcloning of yeast genes on small DNA fragments.

We have constructed three new subcloning plasmid vectors, pRC1, pRC2, and pRC3, derived from pKC7, which allow the rapid, single-step subcloning of yeast genes. Subcloning with these vectors utilizes a partial digestion with Sau3A to generate a quasi-random set of DNA fragments from the original plasmid. All three vectors contain a kanamycin resistance gene. Therefore, if the original cloned yeast DNA fragment is present in a vector that does not specify kanamycin resistance, the subclone pool can be propagated in Escherichia coli in the presence of kanamycin to select against parent plasmids that escaped restriction by Sau3A. Selection by complementation in yeast yields a collection of plasmids with smaller yeast DNA inserts containing the gene of interest. In the vectors pRC2 and pRC3, constructed from pRC1, the unique BamHI site is located within an intact tetracycline resistance gene, thus making it possible to screen bacterial transformants for those containing recombinant plasmid molecules. Vectors pRC2 and pRC3 also contain the yeast 2 micrometers DNA replication origin, and thus are more stable than plasmids carrying only the TRP1-associated replicator (ars1).

Cloning, Molecular↗
PubMed1981

Use of cycloheximide to study independent lipid metabolism of Chlamydia trachomatis cultivated in mouse L cells grown in serum-free medium.

A system for measuring chlamydial lipid synthesis was developed with mouse L cells grown in serum-free modified Waymouth 752/l medium in a shaker culture. Host lipid synthesis was reduced approximately 90% when cells were incubated for 24 h in medium containing cycloheximide (2 micrograms/ml). Lipid metabolism was monitored by measuring the incorporation of [3H]isoleucine into the total lipid of normal and infected cells. The results suggested that lipid synthesis of Chlamydia trachomatis lymphogranuloma venereum (LGV-404L) was not inhibited by cycloheximide treatment when the chlamydiae were grown in L cells, whereas host lipid synthesis was inhibited. Chlamydial lipid metabolism began about 6 to 12 h after infection when the noninfectious reticulate body was found and continually increased until the beginning of the appearance of intracellular infectious elementary bodies at 24 to 30 h.

Animals↗
PubMed1980

Isolation of genes by complementation in yeast: molecular cloning of a cell-cycle gene.

cdc28, one of several genes required for cell division in the yeast Saccharomyces cerevisiae, has been isolated on recombinant plasmids. A recombinant plasmid pool containing the entire yeast genome was constructed by partial digestion of yeast DNA with the four-base recognition restriction endonuclease Sau3A to give the equivalent of random fragments, size selection on sucrose gradients, and introduction of the fragments into the yeast vector YRp7 by use of the homology of Sau3A ends with those generated in the vector by cleavage with BamHI. Recombinant plasmids capable of complementing cdc28 mutations were isolated by transformation of a cdc28ts strain and selection for clones capable of growth at the restrictive temperature. Plasmids responsible for complementing the cdc28ts phenotype were shown to recombine specifically with the chromosomal cdc28 locus, confirming the identity of the cloned sequences. In addition, one of the recombinant plasmids was capable of complementing a mutation in tyr1, a gene genetically linked to cdc28. This method of gene isolation and identification should be applicable to all yeast genes for which there are readily scorable mutants.

Cell Cycle↗
PubMed1980

The selection of S. cerevisiae mutants defective in the start event of cell division.

Thirty-three temperature-sensitive mutations defective in the start event of the cell division cycle of Saccharomyces cerevisiae were isolated and subjected to preliminary characterization. Complementation studies assigned thes mutations to four complementation groups, one of which, cdc28, has been described previously. Genetic analysis revealed that these complementation groups define single nuclear genes, unlinked to one another. One of the three newly identified genes, cdc37, has been located in the yeast linkage map on chromosome IV, two meiotic map units distal to hom2.--Each mutation produces stage-specific arrest of cell division at start, the same point where mating pheromone interrupts division. After synchronization at start by incubation at the restrictive temperature, the mutants retain the capacity to enlarge and to conjugate.

Cell Division↗
PubMed1980

The selection of amber mutations in genes required for completion of start, the controlling event of the cell division cycle of S. cerevisiae.

Using a modification of a procedure developed for the isolation of temperature-sensitive mutants defective in the start event of cell division, amber mutations were obtained for two Class-I start genes, cdc28 and cdc37. Genetic analysis demonstrated that co-segregation of an amber suppressor with such alleles was required for viability of spores subsequent to meiosis. These mutations are expected to be useful in the identification of the molecular products of the genes cdc28 and cdc37.

Alleles↗
PubMed1980

The effect of cortisol on glycogen and fructose-1,6-bisphosphatase in baby hamster kidney cells infected with Chlamydia trachomatis.

This study was designed to assay changes in glycogen synthesis which may occur as a result of cortisol treatment of chlamydial-infected cells. Monolayers of baby hamster kidney (BHK) cells, unlabeled and prelabeled with [6-14C]glucose, were treated with various concentrations of cortisol before (pretreated) or during (post-treated) infection with Chlamydia trachomatis. At designated times after absorption, the cells were harvested and assayed for total glycogen and 14C accumulation in glycogen. The total amount of glycogen accumulated in cells during the period of greatest chlamydial glycogen synthesis (36 h) was not affected by cortisol treatment. Cortisol treatment appeared to have retarded the accumulation of glycogen in treated infected cells until 30 h after infection. Treated infected cells prelabeled with [6-14C]glucose accumulated a greater amount of 14C in glycogen than untreated infected cells. All cortisol-treated, infected cells exhibited elevated levels of fructose-1,6-bisphosphatase activity, whereas untreated infected cells did not. The hypothesis that cortisol affects chlamydia multiplication by altering the intracellular environment of the host cell is compatible with the results obtained.

Cells, Cultured↗
PubMed1977

Characterization of the autoregulation of simian virus 40 gene A.

Cells infected by tsA mutants of simian virus 40 (SV40) overproduce early RNA. Overproduction results from failure of the temperature-sensitive A protein (T antigen) to inhibit early transcription. The amount of early RNA in the cytoplasm, determined quantitatively from the kinetics of hybridization to labeled complementary SV40 DNA, was elevated at both permissive (32 degrees C) and nonpermissive (41 degrees C) temperatures in all the early mutants tested (tsA7, -30, -58, and -209), but not in the late mutant tsB4. The amount of early RNA in a culture maintained at 32 degrees C for 72 h and then shifted to 41 degrees C was maximum when each cell was infected initially with at least one plaque-forming unit of tsA58. Azidocytidine (2'-deoxy-2'-azidocytidine), which inhibits initiation of DNA synthesis, did not cause overproduction of early RNA in cells infected with wild-type SV40, showing that the effect seen with tsA mutants is not due to interference with initiation of DNA synthesis per se. In parallel infections at 41 degrees C, the amount of early RNA per copy of viral DNA was as much as 2,000 times greater with tsA58 than with wild-type SV40, even though there was no replication of the tsA58 DNA. Synthesis of late RNA could not be detected during the first 20 h of an infection by either virus at 32 degrees C, indicating that late and early transcription are under different control. In three cell lines transformed by tsA mutants, the amount of early RNA increased moderately after a shift from 32 to 41 degrees C, whereas with homologous cells transformed by wild-type virus, the amount of early RNA decreased, indicating that the A protein may be able to repress transcription of integrated SV40 DNA. All the observations are consistent with a simple model in which the binding of A protein at the origin of replication blocks either binding of RNA polymerase to the early promoter or its progress through the early gene(s).

Azides↗
PubMed1976

Autoregulation of simian virus 40 gene A by T antigen.

During lytic infection by simian virus 40, gene A is transcribed into early RNA, which is translated into A protein (T antigen). Both the rate of synthesis and the intracellular amount of early RNA are higher in cells infected by temperature-sensitive A (tsA) mutants than in cells infected by wild-type virus. These differences are observed at permissive temperature (32 degrees) and are amplified greatly after a shift to restrictive temperature (41 degrees). For example, at 32 degrees cells infected by tsA mutants synthesize early RNA approximately twice as fast as cells infected by wild-type virus. After the shift to 41 degrees, the rate of synthesis in the tsA infection increases to 15 times the rate in the wild-type infection. In contrast, cells infected by tsA mutants do not overproduce late RNA. We suggest that the A protein regulates its own synthesis by negative feedback control of gene A transcription.

Antigens, Viral↗
PubMed1975

T antigen binds to simian virus 40 DNA at the origin of replication.

A technique employing ferritin-conjugated antibody has been developed to visualize specific protein-DNA complexes in the electron microscope and has been used to demonstrate the preferential binding of simian virus 40 (SV40) T antigen at or near the origin of replication of SV40 DNA, 0.67 fractional length clockwise from the EcoRI restriction endonuclease cleavage site. urified covalently closed supercoiled circles of SV40DNA were treated with partially purified T antigen and the complex was stabilized by crosslinking with glutaraldehyde. Hamster antiT antigen gamma-globulin, ferritin-labeled goat anti-hamster gamma-globulin, and glutaraldehyde were then added sequentially. The location of the bound ferritin cores was measured with respect to the EcoRI cleavage site and the orientation of the cores relative to the ends of the DNA was determined with respect to the locations of Escherichia coli DNA unwinding protein, which binds to covalently closed supercoiled SV40 DNA at either of two preferred sites, 0.46 or 0.90 fractional length clockwide from the EcoRI cleavage site.

Antigens, Viral↗