Telomeres of polytene chromosomes in a ciliated protozoan terminate in duplex DNA loops - PubMed (original) (raw)

Telomeres of polytene chromosomes in a ciliated protozoan terminate in duplex DNA loops

K G Murti et al. Proc Natl Acad Sci U S A. 1999.

Abstract

The end of a telomeric DNA sequence isolated from a polytene chromosome of a hypotrichous ciliate folds back and hybridizes with downstream telomeric sequence to form a t loop that is stable in the absence of protein and DNA cross-linking. The single-stranded, telomeric DNA sequence at the end of a macronuclear molecule does not form a t loop but, instead, is complexed with a heterodimeric, telomere-binding protein. Thus, two mechanisms for capping the ends of DNA molecules are used in the same cell.

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Figures

Figure 1

Figure 1

Electron micrograph of a collection of duplex loops at the molecular ends of polytene chromosome DNA. The arrow points to a single-stranded stretch at the junction of a loop. (Bar = 1 μm.)

Figure 2

Figure 2

Electron micrograph of polytene chromosomes from a developing macronucleus of O. fallax. T, telomere. (Bar = 0.1 μm.)

Figure 3

Figure 3

Electron micrograph of DNA prepared from vegetative macronuclei of O. fallax. (Bar = 1 μm.)

Figure 4

Figure 4

Models of two different mechanisms for capping telomeric repeats in the micronucleus and macronucleus. (A) Formation of a t loop by a fold-back of the telomeric DNA in a micronuclear chromosome. The single-stranded, G-rich 3′ overhang hybridizes with the C-rich chain in a proximal segment of telomere, displacing the original G-rich chain. Redrawn from Griffith et al. (5). (B) Formation of a terminal complex between heterodimeric, telomere-binding protein and the single-stranded, G-rich 3′ overhang of the telomere in a macronuclear DNA molecule. Redrawn from Froelich-Ammon et al. (18).

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References

    1. Prescott D M. Microbiol Rev. 1994;58:233–267. - PMC - PubMed
    1. Klobutcher L A, Swanton M T, Donini P, Prescott D M. Proc Natl. Acad Sci USA. 1981;78:3015–3019. - PMC - PubMed
    1. Jahn C L. Exp Cell Res. 1988;177:162–175. - PubMed
    1. Dawson D, Herrick G. Cell. 1984;36:171–177. - PubMed
    1. Griffith J D, Comeau L, Rosenfield S, Stansel R M, Bianchi A, Moss H, de Lange T. Cell. 1999;97:503–514. - PubMed

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