The Kinetic Complexity of <i>Paramecium</i> Macronuclear Deoxyribonucleic Acid

Soldo, A. T.; Godoy, G. A.

doi:10.1111/j.1550-7408.1972.tb03558.x

Cited by 37 publications

(13 citation statements)

References 29 publications

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“…The results again showed that no rearrangements were correlated with i-antigen expression. (20), and the size of XSA-1 is 44 kb. Assuming that there is one copy of the gene per genome, the amount of type A gene in XSA-1 is 58,000/44, or 1,300 times the amount in the genome.…”

Section: Resultsmentioning

confidence: 99%

Structure and expression of genes for surface proteins in Paramecium.

et al. 1983

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Surface proteins from 11 antigenic types of Paramecium tetraurelia vary in molecular weight from 251,000 to 308,000. The size of a series of polyadenylated RNAs obtained from these types were correlated with the sizes of the proteins and judged to be the mRNAs for the proteins. The mRNAs were used to identify genomic DNA clones containing complementary sequences. The gene for antigen A was present in one copy per genome, and the data suggest that extensive introns were absent. When restriction enzyme digests of DNA from cultures of paramecia with active and inactive genes were probed with portions of the cloned genes, no evidence for rearrangements or changes in gene dosage was found.

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Section: Resultsmentioning

confidence: 99%

Structure and expression of genes for surface proteins in Paramecium.

et al. 1983

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“…In ciliates, satellite DNA has been found in some strains of P. aurelia (Soldo & Godoy, 1972) and in T. pyriformis strain GL (Sueoka, 1961). Gall (1974) and Engberg et al (1974) have shown that macronuclear satellite DNA of T. pyriformis GL corresponds to ribosomal cistrons.…”

Section: Discussion (I) Gc Contentmentioning

confidence: 99%

Macronuclear DNA in Stentor coeruleus: a first approach to its characterization

Pelvat

Haller

1976

Genet. Res.

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SUMMARYThe macronuclei of Stentor coeruleus were isolated on a discontinuous sucrose gradient and their DNA was purified by conventional methods. The GC content was 32 mole %. The DNA banded as a single peak on analytical ultracentrifugation at 1-691 g/cm 3 . The molecular weight of the DNA was 5 x 10 6 to 4 x 10 7 daltons. Genome size determined by DNA-DNA reassociation kinetics was 6 x 10 10 daltons. The macronuclear genome was mostly simple, about 85 % being made of non-repetitive sequences.

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“…Finally, three of the telomere addition sites, represented by clones d48-1, d48-6, and d48-8, are within the relatively G+C-rich coding region of the A surface antigen gene. The Paramecium genome is 29o G+C (24), while the coding region in this area is 36% G+C.…”

Section: Methodsmentioning

confidence: 99%

Developmentally controlled telomere addition in wild-type and mutant paramecia.

1988

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We analyzed sites of macronuclear telomere addition at a single genetic locus in Paramecium tetraurelia. We showed that in homozygous wild-type cells, differential genomic processing during macronuclear development resulted in the A surface antigen gene being located 8, 13, or 26 kilobases upstream from a macronuclear telomere. We describe variable rearrangements that occurred at the telomere 8 kilobases from the A gene. A mutant (d48) that forms a telomere near the 5' end of the A gene was also analyzed. This mutant was shown to create simple terminal deletions; telomeric repeats were added directly to the truncated wild-type A gene sequence. In both the mutant and wild-type cells, the telomeric sequences (a mixture of C4A2 and C3A3 repeats) were added to various sequences within a specific 200-to 500-base-pair region rather than to a single site. No similarities were found in the primary sequences surrounding the telomere addition sites. The mutation in d48 changed the region of telomere addition at the A gene locus; this is the first example in ciliates of a mutation that affects the site of telomere addition.Developmentally controlled formation of new telomeres occurs in diverse eucaryotes. There is cytological evidence for de novo telomere formation in Ascaris and the crustacean Cyclops (reviewed in reference 29) and molecular evidence for its occurrence in ciliated protozoans. Ciliates contain two functionally and morphologically distinct types of nuclei within a single cell. Both types, micronuclei and macronuclei, arise from a single diploid fertilization nucleus during a sexual event. In the ciliate Paramecium tetraurelia, the micronuclei remain diploid and are transcriptionally inactive, while the DNA in the transcriptionally active macronucleus is amplified to about 800C. The formation of the new macronucleus involves the loss and rearrangement of sequences from the germ line DNA as well as chromosomal fragmentation (reviewed in reference 5). Fragmentation of the micronuclear chromosomes during macronuclear development has been well documented in two classes of ciliates, the holotrichous ciliate Tetrahymena (1, 7) and the hypotrichous ciliates (reviewed in reference 16). The resulting linear macronuclear DNA fragments, which we will refer to as macronuclear chromosomes, have telomeric sequences added to their ends. Work by Preer and Preer (20) suggested that fragmentation of micronuclear chromosomes also occurs in P. tetraurelia.The telomeric sequences of several ciliates have been determined. The linear macronuclear chromosomes of two holotrichs, Tetrahymena and Glaucoma, terminate with (C4A2 T2G4) tandem repeats (4,14,31). Hypotrichous ciliates such as Oxytricha have C4A4 repeats on their macronuclear DNA ends (17). In both cases the telomeric repeats are highly homogeneous, with no sequence variation. Several lines of evidence from both holotrichs and hypotrichs support the idea that during macronuclear development telomeric repeats are added de novo to the nontelomeric sequence at the ends of new...

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The Kinetic Complexity of Paramecium Macronuclear Deoxyribonucleic Acid

Cited by 37 publications

References 29 publications

Structure and expression of genes for surface proteins in Paramecium.

Structure and expression of genes for surface proteins in Paramecium.

Macronuclear DNA in Stentor coeruleus: a first approach to its characterization

Developmentally controlled telomere addition in wild-type and mutant paramecia.

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