Evidence for Darwinian selection of the 2-μm plasmid STB locus in Saccharomyces cerevisiae

Genome ◽  
1994 ◽  
Vol 37 (1) ◽  
pp. 12-18 ◽  
Author(s):  
G. H. Rank ◽  
W. Xiao ◽  
G. M. Arndt
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasmid Stability ◽  
Type I ◽  
Type Ii ◽  
Haploid Strain ◽  
Unique Region ◽  
Cis Acting ◽  
Plasmid Partition ◽  
Wine Strain ◽  
2 Μm Plasmid

The 2-μm plasmid of industrial and laboratory strains of Saccharomyces cerevisiae exists as two main polymorphic forms designated type I and type II. Polymorphism is restricted to the 3200-bp right unique region where types I and II show approximately 10% nucleotide divergence in trans-acting REP1 and RAF loci and 30% divergence in the cis-acting STB locus. In addition, the cis-acting STB plasmid partition locus of type II plasmids varies in sequence and copy number of a 125-bp repeat. We devised chimeric and 2-μm plasmid stability experiments to evaluate the effect of STB polymorphism on plasmid fitness in amphiploid industrial and haploid laboratory strains. Reciprocal experiments of type-II STB chimeric plasmids in type-I bakers' yeast or a type-I chimeric plasmid in type-II distillers', wine, or haploid strains showed similar partition efficiencies. However, chimeric and 2-μm plasmids carrying a 250-bp STB from a type-II haploid strain had reduced fitness in a type-II industrial wine strain. These results in conjunction with molecular analyses of 2-μm-like and 2-μm plasmids indicates the coevolution of STB with trans-acting plasmid and host-cell factors.Key words: Saccharomyces cerevisiae, 2-μm plasmid, STB adaption.

scholarly journals Partitioning of the 2-μm Circle Plasmid of Saccharomyces cerevisiae

2000 ◽  
Vol 149 (3) ◽  
pp. 553-566 ◽  
Author(s):  
Soundarapandian Velmurugan ◽  
Xian-Mei Yang ◽  
Clarence S.-M. Chan ◽  
Melanie Dobson ◽  
Makkuni Jayaram
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Yeast Cells ◽  
Cis Acting ◽  
Plasmid Segregation ◽  
Daughter Cells ◽  
Chromosomal Segregation ◽  
Rep Proteins ◽  
Cellular Machinery ◽  
2 Μm Plasmid ◽  
Kinetics Of

The efficient partitioning of the 2-μm plasmid of Saccharomyces cerevisiae at cell division is dependent on two plasmid-encoded proteins (Rep1p and Rep2p), together with the cis-acting locus REP3 (STB). In addition, host encoded factors are likely to contribute to plasmid segregation. Direct observation of a 2-μm–derived plasmid in live yeast cells indicates that the multiple plasmid copies are located in the nucleus, predominantly in clusters with characteristic shapes. Comparison to a single-tagged chromosome or to a yeast centromeric plasmid shows that the segregation kinetics of the 2-μm plasmid and the chromosome are quite similar during the yeast cell cycle. Immunofluorescence analysis reveals that the plasmid is colocalized with the Rep1 and Rep2 proteins within the yeast nucleus. Furthermore, the Rep proteins (and therefore the plasmid) tend to concentrate near the poles of the yeast mitotic spindle. Depolymerization of the spindle results in partial dispersion of the Rep proteins in the nucleus concomitant with a loosening in the association between plasmid molecules. In an ipl1-2 yeast strain, shifted to the nonpermissive temperature, the chromosomes and plasmid almost always missegregate in tandem. Our results suggest that, after DNA replication, plasmid distribution to the daughter cells occurs in the form of specific DNA-protein aggregates. They further indicate that the plasmid partitioning mechanism may exploit at least some of the components of the cellular machinery required for chromosomal segregation.

scholarly journals The Rad51 Pathway of Telomerase-Independent Maintenance of Telomeres Can Amplify TG1-3 Sequences in yku and cdc13 Mutants of Saccharomyces cerevisiae

2003 ◽  
Vol 23 (11) ◽  
pp. 3721-3734 ◽  
Author(s):  
Nathalie Grandin ◽  
Michel Charbonneau
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chromosome Instability ◽  
Type I ◽  
Type Ii ◽  
Wild Type ◽  
Delayed Senescence ◽  
Parallel Pathways ◽  
Crisis Events ◽  
Resistant Cells

ABSTRACT In the yeast Saccharomyces cerevisiae, Cdc13, Yku, and telomerase define three parallel pathways for telomere end protection that prevent chromosome instability and death by senescence. We report here that cdc13-1 yku70Δ mutants generated telomere deprotection-resistant cells that, in contrast with telomerase-negative senescent cells, did not display classical crisis events. cdc13-1 yku70Δ cells survived telomere deprotection by exclusively amplifying TG1-3 repeats (type II recombination). In a background lacking telomerase (tlc1Δ), this process predominated over type I recombination (amplification of subtelomeric Y′ sequences). Strikingly, inactivation of the Rad50/Rad59 pathway (which is normally required for type II recombination) in cdc13-1 yku70Δ or yku70Δ tlc1Δ mutants, but also in cdc13-1 YKU70+ tlc1Δ mutants, still permitted type II recombination, but this process was now entirely dependent on the Rad51 pathway. In addition, delayed senescence was observed in cdc13-1 yku70Δ rad51Δ and cdc13-1 tlc1Δ rad51Δ cells. These results demonstrate that in wild-type cells, masking by Cdc13 and Yku prevents the Rad51 pathway from amplifying telomeric TG1-3 sequences. They also suggest that Rad51 is more efficient than Rad50 in amplifying the sequences left uncovered by the absence of Cdc13 or Yku70.

scholarly journals Telomere-Telomere Recombination Is an Efficient Bypass Pathway for Telomere Maintenance in Saccharomyces cerevisiae

1999 ◽  
Vol 19 (12) ◽  
pp. 8083-8093 ◽  
Author(s):  
Shu-Chun Teng ◽  
Virginia A. Zakian
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Structural Changes ◽  
Telomere Maintenance ◽  
Type I ◽  
Type Ii ◽  
Human Cell Lines ◽  
Wild Type ◽  
Telomeric Dna ◽  
Cell Divisions ◽  
Continuous Presence

ABSTRACT Many Saccharomyces telomeres bear one or more copies of the repetitive Y′ element followed by ∼350 bp of telomerase-generated C1–3A/TG1–3 repeats. Although most cells lacking a gene required for the telomerase pathway die after 50 to 100 cell divisions, survivors arise spontaneously in such cultures. These survivors have one of two distinct patterns of telomeric DNA (V. Lundblad and E. H. Blackburn, Cell 73:347–360, 1993). The more common of the two patterns, seen in type I survivors, is tandem amplification of Y′ followed by very short tracts of C1–3A/TG1–3 DNA. By determining the structure of singly tagged telomeres, chromosomes in type II survivors were shown to end in very long and heterogeneous-length tracts of C1–3A/TG1–3 DNA, with some telomeres having 12 kb or more of C1–3A/TG1–3 repeats. Maintenance of these long telomeres required the continuous presence of Rad52p. Whereas type I survivors often converted to the type II structure of telomeric DNA, the type II pattern was maintained for at least 250 cell divisions. However, during outgrowth, the structure of type II telomeres was dynamic, displaying gradual shortening as well as other structural changes that could be explained by continuous gene conversion events with other telomeres. Although most type II survivors had a growth rate similar to that of telomerase-proficient cells, their telomeres slowly returned to wild-type lengths when telomerase was reintroduced. The very long and heterogeneous-length telomeres characteristic of type II survivors in Saccharomyces are reminiscent of the telomeres in immortal human cell lines and tumors that maintain telomeric DNA in the absence of telomerase.

Heat-Etching with a Bullivant Type II Simple Freeze-Cleave Device

1970 ◽  
Vol 28 ◽  
pp. 106-107 ◽  
Author(s):  
Ronald S. Weinstein ◽  
N. Scott McNutt
Keyword(s):  
New Zealand ◽  
General Hospital ◽  
Massachusetts General Hospital ◽  
Type I ◽  
Type Ii ◽  
Collaborative Effort ◽  
Temperature And Pressure ◽  
The University

The Type I simple cold block device was described by Bullivant and Ames in 1966 and represented the product of the first successful effort to simplify the equipment required to do sophisticated freeze-cleave techniques. Bullivant, Weinstein and Someda described the Type II device which is a modification of the Type I device and was developed as a collaborative effort at the Massachusetts General Hospital and the University of Auckland, New Zealand. The modifications reduced specimen contamination and provided controlled specimen warming for heat-etching of fracture faces. We have now tested the Mass. General Hospital version of the Type II device (called the “Type II-MGH device”) on a wide variety of biological specimens and have established temperature and pressure curves for routine heat-etching with the device.

Labelling of non-A, non-B hepatitis infected chimpanzee hepatocytes with nuclease-gold conjugates

1984 ◽  
Vol 42 ◽  
pp. 250-251
Author(s):  
G. D. Gagne ◽  
M. F. Miller ◽  
D. A. Peterson
Keyword(s):  
Endoplasmic Reticulum ◽  
Experimental Infection ◽  
Uranyl Acetate ◽  
Type I ◽  
Cellular Injury ◽  
Type Ii ◽  
Tubular Structures ◽  
Type Iii ◽  
Type Iv ◽  
Infected Chimpanzee

Experimental infection of chimpanzees with non-A, non-B hepatitis (NANB) or with delta agent hepatitis results in the appearance of characteristic cytoplasmic alterations in the hepatocytes. These alterations include spongelike inclusions (Type I), attached convoluted membranes (Type II), tubular structures (Type III), and microtubular aggregates (Type IV) (Fig. 1). Type I, II and III structures are, by association, believed to be derived from endoplasmic reticulum and may be morphogenetically related. Type IV structures are generally observed free in the cytoplasm but sometimes in the vicinity of type III structures. It is not known whether these structures are somehow involved in the replication and/or assembly of the putative NANB virus or whether they are simply nonspecific responses to cellular injury. When treated with uranyl acetate, type I, II and III structures stain intensely as if they might contain nucleic acids. If these structures do correspond to intermediates in the replication of a virus, one might expect them to contain DNA or RNA and the present study was undertaken to explore this possibility.

Comparative surface and ultrastructural views of methylotrophic bacteria by TEM, STEM, SE, and freeze-etch electron microscopy.

1987 ◽  
Vol 45 ◽  
pp. 792-793
Author(s):  
T.A. Fassel ◽  
M.J. Schaller ◽  
M.E. Lidstrom ◽  
C.C. Remsen
Keyword(s):  
Cytoplasmic Membrane ◽  
Structural Features ◽  
Methylotrophic Bacteria ◽  
Type I ◽  
Type Ii ◽  
Membrane Complex ◽  
Oxidation Of Methane ◽  
Methane Oxidizing Bacteria ◽  
Wall Structures ◽  
Methylomonas Albus

Methylotrophic bacteria play an Important role in the environment in the oxidation of methane and methanol. Extensive intracytoplasmic membranes (ICM) have been associated with the oxidation processes in methylotrophs and chemolithotrophic bacteria. Classification on the basis of ICM arrangement distinguishes 2 types of methylotrophs. Bundles or vesicular stacks of ICM located away from the cytoplasmic membrane and extending into the cytoplasm are present in Type I methylotrophs. In Type II methylotrophs, the ICM form pairs of peripheral membranes located parallel to the cytoplasmic membrane. Complex cell wall structures of tightly packed cup-shaped subunits have been described in strains of marine and freshwater phototrophic sulfur bacteria and several strains of methane oxidizing bacteria. We examined the ultrastructure of the methylotrophs with particular view of the ICM and surface structural features, between representatives of the Type I Methylomonas albus (BG8), and Type II Methylosinus trichosporium (OB-36).

OPTICAL STUDIES OF TYPE I AND TYPE II RECOMBINATION IN GaAs-AlAs QUANTUM WELLS

1987 ◽  
Vol 48 (C5) ◽  
pp. C5-525-C5-528 ◽  
Author(s):  
K. J. MOORE ◽  
P. DAWSON ◽  
C. T. FOXON
Keyword(s):  
Quantum Wells ◽  
Type I ◽  
Type Ii ◽  
Optical Studies

An old friend is better than two new ones? Approaches to market research in the context of digital transformation for the antitrust laws enforcement

2020 ◽  
pp. 37-55 ◽  
Author(s):  
A. E. Shastitko ◽  
O. A. Markova
Keyword(s):  
Business Models ◽  
Rapid Development ◽  
Digital Transformation ◽  
Market Definition ◽  
Type I ◽  
Type Ii ◽  
Digital Platforms ◽  
Advantages And Disadvantages ◽  
Pass Through ◽  
Type Ii Errors

Digital transformation has led to changes in business models of traditional players in the existing markets. What is more, new entrants and new markets appeared, in particular platforms and multisided markets. The emergence and rapid development of platforms are caused primarily by the existence of so called indirect network externalities. Regarding to this, a question arises of whether the existing instruments of competition law enforcement and market analysis are still relevant when analyzing markets with digital platforms? This paper aims at discussing advantages and disadvantages of using various tools to define markets with platforms. In particular, we define the features of the SSNIP test when being applyed to markets with platforms. Furthermore, we analyze adjustment in tests for platform market definition in terms of possible type I and type II errors. All in all, it turns out that to reduce the likelihood of type I and type II errors while applying market definition technique to markets with platforms one should consider the type of platform analyzed: transaction platforms without pass-through and non-transaction matching platforms should be tackled as players in a multisided market, whereas non-transaction platforms should be analyzed as players in several interrelated markets. However, if the platform is allowed to adjust prices, there emerges additional challenge that the regulator and companies may manipulate the results of SSNIP test by applying different models of competition.

Sign in / Sign up

Export Citation Format

Share Document