AW Murray, TE Claus, and JW Szostak. 1988. “Characterization of two telomeric DNA processing reactions in Saccharomyces cerevisiae.” Mol Cell Biol, 8, 11, Pp. 4642-50. Publisher's VersionAbstract
We have investigated two reactions that occur on telomeric sequences introduced into Saccharomyces cerevisiae cells by transformation. The elongation reaction added repeats of the yeast telomeric sequence C1-3A to telomeric sequences at the end of linear DNA molecules. The reaction worked on the Tetrahymena telomeric sequence C4A2 and also on the simple repeat CA. The reaction was orientation specific: it occurred only when the GT-rich strand ran 5' to 3' towards the end of the molecule. Telomere elongation occurred by non-template-directed DNA synthesis rather than any type of recombination with chromosomal telomeres, because C1-3A repeats could be added to unrelated DNA sequences between the CA-rich repeats and the terminus of the transforming DNA. The elongation reaction was very efficient, and we believe that it was responsible for maintaining an average telomere length despite incomplete replication by template-directed DNA polymerase. The resolution reaction processed a head-to-head inverted repeat of telomeric sequences into two new telomeres at a frequency of 10(-2) per cell division.
AW Murray. 1988. “A mitotic inducer matures.” Nature, 335, 6187, Pp. 207-8. Publisher's Version
AW Murray and JW Szostak. 1987. “Artificial chromosomes.” Sci Am, 257, 5, Pp. 62-8. Publisher's Version
AW Murray. 1987. “Cell biology. Cyclins in meiosis and mitosis.” Nature, 326, 6113, Pp. 542-3. Publisher's Version
AW Murray. 1987. “Cell cycle control. A cycle is a cycle is a cycle.” Nature, 327, 6117, Pp. 14-5. Publisher's Version
CI Pretzman, Y Rikihisa, D Ralph, JC Gordon, and S Bech-Nielsen. 1987. “Enzyme-linked immunosorbent assay for Potomac horse fever disease.” J Clin Microbiol, 25, 1, Pp. 31-6. Publisher's VersionAbstract
An enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G (IgG) and IgM in natural and experimental infections of equids with Ehrlichia risticii was developed. Ehrlichial organisms purified from an infected mouse macrophage cell line were used as the antigen. IgM was separated from serum IgG by the expedient of spun-column chromatography, allowing the use of an indirect ELISA for quantitation of both IgG and IgM in the test sera. Among 16 paired sera from horses exhibiting clinical signs of Potomac horse fever, 8 were positive by the indirect fluorescent-antibody test (IFA), 11 were positive by the IgG ELISA, and 8 were positive by the IgM ELISA. All IFA-positive specimens were positive by the IgG ELISA, which appeared to be more sensitive than the IFA. In all cases, the IgG ELISA alone would have sufficed for diagnosis when acute- and convalescent-phase sera were available. When 26 single acute- or convalescent-phase serum samples were tested, the IFA detected 8, the IgG ELISA detected 10, and the IgM ELISA detected 6 positive serum specimens. The kinetics of IgG and IgM responses as determined by ELISA in two experimentally infected ponies which survived infection and challenges revealed that specific IgM was short-lived, falling to undetectable levels by day 60 postinoculation, whereas specific IgG persisted for more than 1 year. IgM and IgG were detected as early as days 1 and 10, respectively, postinoculation. The results suggest that the ELISA is more sensitive than the IFA and that the IgM ELISA may provide a means for early diagnosis of Potomac horse fever at or before the onset of clinical signs.
AE Reynolds, AW Murray, and JW Szostak. 1987. “Roles of the 2 microns gene products in stable maintenance of the 2 microns plasmid of Saccharomyces cerevisiae.” Mol Cell Biol, 7, 10, Pp. 3566-73. Publisher's VersionAbstract
We have examined the replication and segregation of the Saccharomyces cerevisiae 2 microns circle. The amplification of the plasmid at low copy numbers requires site-specific recombination between the 2 microns inverted repeat sequences catalyzed by the plasmid-encoded FLP gene. No other 2 microns gene products are required. The overexpression of FLP in a strain carrying endogenous 2 microns leads to uncontrolled plasmid replication, longer cell cycles, and cell death. Two different assays show that the level of Flp activity decreases with increasing 2 microns copy number. This regulation requires the products of the REP1 and REP2 genes. These gene products also act together to ensure that 2 microns molecules are randomly segregated between mother and daughter cells at cell division.
DS Dawson, AW Murray, and JW Szostak. 1986. “An alternative pathway for meiotic chromosome segregation in yeast.” Science, 234, 4777, Pp. 713-7. Publisher's VersionAbstract
In meiosis I of most organisms, homologous chromosomes pair, recombine, and then segregate to opposite poles of the cell. Crossing-over is normally necessary to ensure the proper segregation of the homologs. Recently developed techniques have made it possible to study meiosis with highly defined artificial chromosomes. These techniques were used to demonstrate the existence of a system capable of segregating pairs of nonrecombined artificial chromosomes, regardless of the extent of their sequence homology. This system may contribute to the high fidelity of meiosis by mediating the segregation of pairs of natural chromosomes that have failed to recombine.
AW Murray, NP Schultes, and JW Szostak. 1986. “Chromosome length controls mitotic chromosome segregation in yeast.” Cell, 45, 4, Pp. 529-36. Publisher's VersionAbstract
We have examined the effect of physical length on the mitotic segregation of artificial chromosomes and fragments of natural yeast chromosomes. Increasing the length of artificial chromosomes decreases the rate at which they are lost during mitosis. We have made fragments of chromosome III by integrating new telomeres at different positions along the length of the chromosome. Chromosome fragments of 42 and 72 kb behave like artificial chromosomes: they are lost in mitosis much more frequently than natural chromosomes. In contrast, a chromosome fragment of 150 kb is as mitotically stable as the full-length chromosome from which it is derived. The structural instability of a short dicentric artificial chromosome demonstrates that, although short artificial chromosomes segregate poorly in mitosis, they do attach to the mitotic spindle. We discuss these results in the context of a model in which chromosome segregation is directed by the intercatenation of the segregating DNA molecules.
AW Murray and JW Szostak. 1986. “Construction and behavior of circularly permuted and telocentric chromosomes in Saccharomyces cerevisiae.” Mol Cell Biol, 6, 9, Pp. 3166-72. Publisher's VersionAbstract
We developed techniques that allow us to construct novel variants of Saccharomyces cerevisiae chromosomes. These modified chromosomes have precisely determined structures. A metacentric derivative of chromosome III which lacks the telomere-associated X and Y' elements, which are found at the telomeres of most yeast chromosomes, behaves normally in both mitosis and meiosis. We made a circularly permuted telocentric version of yeast chromosome III whose closest telomere was 33 kilobases from the centromere. This telocentric chromosome was lost at a frequency of 1.6 X 10(-5) per cell compared with a frequency of 4.0 X 10(-6) for the natural metacentric version of chromosome III. An extremely telocentric chromosome whose closet telomere was only 3.5 kilobases from the centromere was lost at a frequency of 6.0 X 10(-5). The mitotic stability of telocentric chromosomes shows that the very high frequency of nondisjunction observed for short linear artificial chromosomes is not due to inadequate centromere-telomere separation.
AW Murray and JW Szostak. 1985. “Chromosome segregation in mitosis and meiosis.” Annu Rev Cell Biol, 1, Pp. 289-315. Publisher's Version
AW Murray. 1985. “Chromosome structure and behavior.” Trends in Biochemical Sciences, 10, 3, Pp. 112-115. Publisher's Version
SK Weller, A Spadaro, JE Schaffer, AW Murray, AM Maxam, and PA Schaffer. 1985. “Cloning, sequencing, and functional analysis of oriL, a herpes simplex virus type 1 origin of DNA synthesis.” Mol Cell Biol, 5, 5, Pp. 930-42. Publisher's VersionAbstract
The herpes simplex virus type 1 genome (160 kilobases) contains three origins of DNA synthesis: two copies of oriS located within the repeated sequences flanking the short unique arm (US), and one copy of oriL located within the long unique arm (UL). Precise localization and characterization of oriL have been severely hampered by the inability to clone sequences which contain it (coordinates 0.398 to 0.413) in an undeleted form in bacteria. We report herein the successful cloning of sequences between 0.398 to 0.413 in an undeleted form, using a yeast cloning vector. Sequence analysis of a 425-base pair fragment spanning the deletion-prone region has revealed a perfect 144-base pair palindrome with striking homology to oriS. In a functional assay, the undeleted clone was amplified when functions from herpes simplex virus type 1 were supplied in trans, whereas clones with deletions of 55 base pairs or more were not amplified.
JW Szostak, AW Murray, T Claus, and B Dunn. 1984. “Telomeres and artificial chromosomes in yeast.” In Chromosomes Today, 8: Pp. 59-68. London: George, Allen and Unwin. Publisher's Version
SW Ruby, JW Szostak, and AW Murray. 1983. “Cloning regulated yeast genes from a pool of lacZ fusions.” Methods Enzymol, 101, Pp. 253-69. Publisher's Version
AW Murray and JW Szostak. 1983. “Construction of artificial chromosomes in yeast.” Nature, 305, 5931, Pp. 189-93. Publisher's VersionAbstract
Fifty-five-kilobase long artificial chromosomes containing cloned genes, replicators, centromeres and telomeres have been constructed in yeast. These molecules have many of the properties of natural yeast chromosomes. Centromere function is impaired on short (less than 20 kilobases) artificial chromosomes.
AW Murray and JW Szostak. 1983. “Pedigree analysis of plasmid segregation in yeast.” Cell, 34, 3, Pp. 961-70. Publisher's VersionAbstract
We have used pedigree analysis to investigate the mitotic segregation of circular and linear DNA plasmids in Saccharomyces cerevisae. Circular ARS plasmids, which bear putative chromosomal replication origins, have a high segregation frequency and a strong bias to segregate to the mother cell at mitosis. The segregation bias explains how the fraction of plasmid-bearing cells can be small despite the high average copy number of circular ARS plasmids. Linear ARS plasmids do not show strong segregation bias, nor does the 2 mu ori-containing plasmid YEp 13, when it is present in strains containing intact 2 mu circles. In the absence of endogenous 2 mu circles, YEp 13 behaves like an ARS plasmid, showing a strong maternal segregation bias. The presence of a centromere on circular ARS plasmids eliminates segregation bias. We discuss a model for plasmid segregation, which explains these findings and the possible biological significance of mother-daughter segregation bias.
LB Chen, K Burridge, A Murray, ML Walsh, CD Copple, A Bushnell, JK McDougall, and PH Gallimore. 1978. “Modulation of cell surface glycocalyx: studies on large, external, transformation-sensitive protein.” Ann N Y Acad Sci, 312, Pp. 366-81. Publisher's Version
LB Chen, A Murray, R.A. Segal, A Bushnell, and ML Walsh. 1978. “Studies on intercellular LETS glycoprotein matrices.” Cell, 14, 2, Pp. 377-91. Publisher's VersionAbstract
Intercellular matrices secreted by chick embryo fibroblasts in culture were studied by scanning electron microscopy. Cell-cell contact is a prerequisite for the expression of such matrices. The smallest fiber detected by transmission electron microscopy is 5--10 nm in diameter. These matrix fibers tend to cluster to form bundles. Immunofluorescence and immunoferritin procedures reveal that LETS protein is one of the components of the matrices. The matrices are isolated from other cellular organelles by detergent treatment. More than 90% of the proteins in cell-free matrices are LETS protein, suggesting that the matrices are probably made of only one component--LETS protein. Since the solubilization of matrices requires beta-mercaptoethanol, LETS protein matrices may be the first known polymer system in nature to use disulfide linkage as an intermolecular polymerization vehicle. Collagen does not appear to be involved in such matrices. The LETS protein matrix supports the morphological conversion of rounded cells into spindle-shaped, and also promotes myoblast fusion. It does not, however, exert an effect upon cell growth, the rate of glucose uptake or protease production.