Location of Ribosomal RNA Cistrons in Yeast

Finkelstein, David; Blamire, John; Marmur, Julius

doi:10.1038/newbio240279a0

Cited by 66 publications

(24 citation statements)

References 12 publications

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“…Furthermore, the entry into the nucleolus by segments of SC may be taken to represent the karyotypic location of nucleolar organizers. Hybridization of ribosomal RNA to fractionated chromosomal DNA from aneuploid strains suggests the occurrence of more than one chromosome with rDNA sequences (13), the majority of these sequences being on chromosome I (14). Although our inability to follow the SC within the nucleolus prevents determination of overall length (and possible continuities) of bivalents, the unambiguous entry by two segments may well represent the presence of rDNA sequences at the ends of two bivalents.…”

Section: Discussionmentioning

confidence: 99%

Electron microscopic observations on the meiotic karyotype of diploid and tetraploid Saccharomyces cerevisiae.

Byers¹,

Goetsch²

1975

Proc. Natl. Acad. Sci. U.S.A.

156

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Certain strains of Saccharomyces cerevisiae contain visible segments of synaptonemal complex which are apparent components of bivslents in pachytene of meiotic prophase. The synaptonemal complex has the typical width in the frontal plane but is unusually thin in the sagittal plane, thus accounting for its poor visibility. Amorphous densities situated adjacent to the central element occur at intervals suggesting their coincidence with sites of crossing over. Reconstruction of the synaptonemal complex from serial sections has permitted karyotypic analysis. The number of segments of synaptonemal complex and the distribution of their lengths is consistent with the genetic map. Two, possibly three, segments enter the nucleolus as if bearing sequences encoding ribosomal RNA. Reconstruction of tetraploid nuclei reveals an approximate doubling of the diploid chromosome number and confirms the pattern of nucleolar entry. Quadrivalent pairing is evident between the pairs of synaptonemal complex segments in the tetraploid nuclei. Although the budding yeast, Saccharomyces cerevisiae, has proven highly amenable to genetic analysis, cytogenetic analysis has been limited by the absence of a karyotype visible by light microscopy. The greater resolution of electron microscopy has revealed several features of spindle behavior during nuclear division but has failed to reveal the individual chromosomes. Nevertheless, genetic studies of the spores derived from meiosis indicate that yeast chromosomes probably undergo synaptic behavior similar to that of other eukaryotes. Meiotic nuclei have occasionally been found to contain the synaptonemal complex (SC) both in aggregates and as individual segments (1, 2). Recent observations by Zickler and Olson (3) demonstrate the typical phases of meiosis in yeast, confirming that the individual segments of SC represent components of pachytene bivalents as they do in other species. We have now achieved serial section electron microscopy of meiotic yeast adequate for reconstructing the distribution of these segments of the synaptonemal complex. On this basis, we report here the numbers and lengths of meiotic chromosomes in diploid and tetraploid strains of S. cerevisiae. MATERIALS AND METHODSStrains. The original diploid strain used for these observations is strain 212-1, constructed by Simchen (4). It is homozygous for the temperature-sensitive cell division cycle allele cdc 4-3 (5). This strain sporulates well, forming over 75% four-spored asci with viable spores after transfer from acetate growth medium to sporulation medium under permissive conditions, as described by Simchen (4). The tetraploid derivative, 212-1-T, was obtained by crossing clones that had been induced by UV irradiation to become capable of mating (by conversion of the mating type to aa or aa); the latter were generously supplied by Ms. Hannah Klein. The Abbreviation: SC, synaptonemal complex. cells of 212-1-T were significantly larger than 212-1 and sporulated equally well at the permissive temperature (200), which w...

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Section: Discussionmentioning

confidence: 99%

Electron microscopic observations on the meiotic karyotype of diploid and tetraploid Saccharomyces cerevisiae.

Byers¹,

Goetsch²

1975

Proc. Natl. Acad. Sci. U.S.A.

156

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“…Secondly oDNA is cytoplasmic and its size of 4.02 x 106 daltons [18] is insufficient to code for a molecule of precursor ribosomal RNA with a double-stranded molecular weight of 5.0 x 106 [28,29]. The third reason against a ribosomal DNA function is that total oDNA (allowing for the molecular weight of oligomeric forms) comprises only 2.9O/, of the genome, whereas ribosomal DNA represents 7 o/o [27].…”

Section: Dna From Purified Nuclei Of 2ee-lmentioning

confidence: 99%

Localization and Quantification of Circular DNA in Yeast

Clark-Walker

Miklos

1974

European Journal of Biochemistry

123

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Xaccharomyces cerevisiae contains 62 molecules per cell of a class of covalently closed circular DNA termed omicron (oDNA) of buoyant density 1.701 g/cm3 with a major size class of 1.9 pm. The localization of oDNA has been investigated in a respiratory deficient mutant 2en-1 containing altered mitochondrial DNA (@DNA) in the form of covalently closed circles. There are 81 @DNA molecules per cell and they range in size from 0.05 pm to 1.6 pm and have a buoyant density of 1.676 g/cm3. When this mini-circular @DNA is used as a marker of cytoplasmic contamination, we find that purified nuclei do not contain oDNA. We conclude from the cytoplasmic location of oDNA that it does not represent a gene amplification product nor is it related to "informosomal" DNA.The discovery in the yeast Saccharomyces cerevisiae of a class of non-mitochondria1 covalently closed circular DNA termed omicron (oDNA), has we feel, a direct bearing on the current debate concerning gene amplification and informosomal DNA. It has been claimed on the one hand that oDNA is located in the nucleus [ 11, whereas evidence has also been presented that it can be recovered from a cytoplasmic fraction free of nuclei [2]. oDNA could therefore fulfill one of the criteria for informosomal DNA, which involves the formation of copies of chromosomal genes followed by their transport to the cytoplasm [3-51. I n this regard several authors have reported the occurrence of non-mitochondria1 cytoplasmic DNA in a variety of organisms [6-111, including yeast [12,2], and claims have been made for a nuclear origin for membrane-associated cytoplasmic DNA in cultured human cells [13]. Also a pertinent observation is that of Smith and Vinograd Ell] who have found a cytoplasmically occurring heterodisperse species of covalently closed circular DNA in HeLa cells with the buoyant density of main band DNA. Although this DNA is located in the cytoplasm, these authors have argued that it has a nuclear origin. However, the existence of informosomal DNA has been questioned by others and their criticisms have generally been based on evidence which suggests that this DNA is an artefact produced by degradation of nuclei [ 14 -171.Trivial name. Ethidium bromide, 3,8-diamino-5-ethyl-6-phenylphenanthridinium bromide.Eur. J. Biochem. 41 (1974) Yeast may therefore be useful in resolving these difficulties. Two observations in addition to the abovementioned report [l] have led us to consider a possible nuclear origin for oDNA. First, it has the same buoyant density as nuclear DNA, and second, it is not eliminated by growth limiting concentrations of ethidium bromide which eliminate mitochondrial DNA [ Z ] .If the circular DNA in yeast is nuclear, a stringent criterion is necessary for determining cytoplasmic contamination of nuclei. We therefore used a petite strain which retained its mitochondrial @DNA in the form of small heterodisperse covalently closed circular molecules. The presence of these mini circles in DNA preparations is used as an index of cytoplasmic contamination of nuc...

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“…Several research groups (7)(8)(9) have obtained evidence suggesting that many of the rDNA genes are located on chromosome I. In this report, I reinvestigated the chromosomal location of the rDNA genes by using the form I-form II rDNA heterogeneity and standard genetic mapping techniques.…”

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confidence: 99%

Yeast ribosomal DNA genes are located on chromosome XII.

Petes¹

1979

Proc. Natl. Acad. Sci. U.S.A.

217

127

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Two lines of experimental evidence indicate that the repeating ribosomal DNA (rDNA) genes of the yeast Saccharomyces cerevisiae are located on chromosome XII. First, the rDNA genes are linked mitotically to genes that have been previously mapped to chromosome XII. Second, yeast strains that have two copies of the chromosome containing the rDNA genes in every strain examined also have two conies of chromosome XII; this is not true for the other yeast chromosomes. These data also establish that in mitosis most of the rDNA genes in yeast are not extrachromosomal.The yeast Saccharomyces cerevisiae has about 100 to 140 copies of the genes coding for ribosomal RNA (1). Although within a single yeast strain the repeating rDNA genes appear to be homogenous (2, 3), among different strains heterogeneity has been detected. Most laboratory strains of yeast contain a single type of rDNA gene, which has seven sites recognized by the EcoRI restriction enzyme (2, 3); this type of rDNA gene has been called the form I rDNA gene (2). Recently, a strain containing only six EcoRI restriction sites per repeating unit (form II rDNA) has been identified (2). The difference between forms I and II rDNA genes is easily detected by agarose gel electrophoresis, and this heterogeneity was used to study the inheritance of the rDNA genes (4, 5). In these experiments, a haploid strain containing form I rDNA was crossed to a haploid strain containing form II rDNA. When the diploid formed by this cross was sporulated, the rDNA heterogeneity in most of the tetrads examined segregated two form I rDNA daughter spores to two form II rDNA daughter spores. This segregation pattern indicated that most and possibly all of the rDNA genes were on a single yeast chromosome.The chromosomal location of the rDNA gene cluster could not be determined in these studies, although the genetic analysis (4, 5) indicated that the rDNA genes were unlinked to the centromere of any of the approximately 17 (6) yeast chromosomes. Several research groups (7-9) have obtained evidence suggesting that many of the rDNA genes are located on chromosome I. In this report, I reinvestigated the chromosomal location of the rDNA genes by using the form I-form II rDNA heterogeneity and standard genetic mapping techniques. I found, by using two independent approaches, that most of the yeast rDNA genes are located on chromosome XII. MATERIALS AND METHODSStrains. The strains used in these studies included: 2262 (a adel ural gall his5 lysll leu2, form II, provided by C. McLaughlin), 661 (a ura2-4 form I, provided by D. Botstein), H17048 (a cdc29 adel ural tyri gall ade2 his7 iys2, form I, from J. Golin), S7(4-2)-4A (a cysi cdcl5 trp5 tyrl ura3 cani R, form I), DL171-477 (a/a ade2/ade2 ADE5/ade5 metl3-c/ metl3-d cyhr/cyhs trp5-c/trp5-d ade6/ADE6 cly8/CLY8The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.cans/cans URA3/ura3 l...

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Location of Ribosomal RNA Cistrons in Yeast

Cited by 66 publications

References 12 publications

Electron microscopic observations on the meiotic karyotype of diploid and tetraploid Saccharomyces cerevisiae.

Electron microscopic observations on the meiotic karyotype of diploid and tetraploid Saccharomyces cerevisiae.

Localization and Quantification of Circular DNA in Yeast

Yeast ribosomal DNA genes are located on chromosome XII.

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