The macronuclear ribosomal DNA of Tetrahymena pyriformis is a palindrome

Karrer, Kathleen M.; Gall, Joseph G.

doi:10.1016/0022-2836(76)90280-1

Cited by 228 publications

(79 citation statements)

References 40 publications

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“…Amplification of palindromic DNA has also been observed in several unicellular eukaryotes including budding and fission yeast, Leishmania, Physarum, and Tetrahymena (12)(13)(14)(15)(16). Studies of ribosomal RNA gene amplification in the ciliated protozoan Tetrahymena have identified critical steps necessary for palindrome formation: a DNA double-stranded break (DSB) occurring near a short inverted-repeat (IR) sequence of 29 bp or longer facilitates an intramolecular recombination between the repeats, which generates a large palindrome after one round of replication ( Fig.…”

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confidence: 99%

Short inverted repeats initiate gene amplification through the formation of a large DNA palindrome in mammalian cells

Tanaka

Tapscott

Trask

et al. 2002

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

108

105

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Gene amplification is a common form of genomic instability in a wide variety of organisms and is often associated with tumor progression in mammals. One striking feature of many amplified genes is their organization as large inverted duplications (palindromes). Here, we describe a molecular mechanism for palindrome formation in mammalian cells that is also conserved in protists. We introduced a short (79 or 229 bp) inverted repeat into the genome of Chinese hamster ovary cells and showed that it promoted the formation of a large DNA palindrome after an adjacent DNA double-strand break. This finding suggests that short inverted repeats in the mammalian genome can have a critical role in the initiation of gene amplification. This specific mechanism may provide a novel target for cancer therapies.

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mentioning

confidence: 99%

Short inverted repeats initiate gene amplification through the formation of a large DNA palindrome in mammalian cells

Tanaka

Tapscott

Trask

et al. 2002

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

108

105

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“…The rRNA genes (rDNA) in the macronucleus of Tetrahymena are extrachromosomal molecules containing about 20,000 base pairs (bp) of DNA (1,2). The linear molecules are palindromic, each half containing a set of rRNA coding sequences and adjacent spacer sequences (3,4). The 10,000 palindromic rDNA molecules in the nucleoli of the macronucleus are probably formed by amplification of a single, nonpalindromic copy integrated in a micronuclear chromosome (5).…”

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confidence: 99%

Localization of transcribed regions on extrachromosomal ribosomal RNA genes of Tetrahymena thermophila by R-loop mapping.

Cech¹,

Rio²

1979

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

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R-loop hybridization and electron microscopy were used to map the RNA transcription products of the extrachromosomal rRNA genes of Tetrahymena thermophila. The mature 17S and 26S rRNAs and the nuclear 35S pre-rRNA and pre-26S rRNA were located with a precision of approximately 100 base pairs. A 370-base pair intervening sequence was found in the 26S coding region. It has the same size and relative location as that found in Tetrahymena pigmentosa [Wild, M. A. & Gall, J. G. (1979) Cell 16, 565-5731. One class of R-loop structures formed by nuclear p&-rRNA provided preliminary evidence for a primary transcript that contains the intervening sequence. The results suggested a processing scheme in which splicing of the intervening sequence is followed by a series of strand cleavages to give the mature 17S and 26S rRNAs. Analysis of the data also showed that RNADNA and DNADNA duplexes, when mounted for electron microscopy by the R-loop procedure, have the same length per base pair within 4%. The rRNA genes (rDNA) in the macronucleus of Tetrahymena are extrachromosomal molecules containing about 20,000 base pairs (bp) of DNA (1, 2). The linear molecules are palindromic, each half containing a set of rRNA coding sequences and adjacent spacer sequences (3, 4). The 10,000 palindromic rDNA molecules in the nucleoli of the macronucleus are probably formed by amplification of a single, nonpalindromic copy integrated in a micronuclear chromosome (5).As one of the few eukaryotic genes that can be isolated in a transcriptionally active chromatin state (6, 7), the Tetrahymena rDNA is of particular interest. For studies of chromatin structure and gene regulation it is necessary to have a detailed transcription map of the rDNA. Previous studies have revealed some general features. Gall et al. (8) showed that transcription proceeds bidirectionally from the central region toward the ends of the molecule. Engberg et al. (4) and Karrer (9) found that the 26S rRNA sequences are distal to the 17S rRNA sequences. Transcription of the smaller rRNA therefore precedes that of the larger rRNA in Tetrahymena as in other organisms (reviewed in ref. 10).The formation of R-loops, regions of RNA-DNA hybridization within a double-stranded DNA molecule, was first described by White and Hogness (11) and Thomas et al. (12). In the present study, we have used R-loop mapping to locate precisely the sequences coding for the mature cytoplasmic rRNAs and the nuclear precursor rRNAs on the rDNA of Tetrahymena thermophila.MATERIALS AND METHODS Growth of Cells. Tetrahymena thermophila strain B VII, obtained from M. Gorovsky, was grown in a medium containing 10 g of proteose peptone (Difco), 30 mg of SequestrineThe 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. 8 M urea (16) and were run at room temperature. RNA in the 8 M urea sample buffer was heated for 5 min at 65°C before being applied to denaturing gels.Isolation of rDNA. Ex...

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“…The size of the average repeat unit is approximately 17.4 kb based on electron microscopy measurements. Thus, the rDNA repeat units in S. bullata are heterogeneous in size like those described for D. melanogaster (6,7,8,9) Xenopus laevis (15), and mouse (5), but unlike those repeats described for Sciara (11), B. mori (17), Tetrahymena (12), and Dictyostellium (14).…”

Section: Discussionmentioning

confidence: 87%

Sequence arrangement of the rRNA genes of the dipteran Sarcophaga bullata

1981

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Velocity sedimentation studies of RNA of Sarcophaga bullata show that the major rRNA species have sedimentation values of 26S and 18S. Analysis of the rRNA under denaturing conditions indicates that there is a hidden break centrally located in the 26S rRNA species. Saturation hybridization studies using total genomic DNA and rRNA show that 0.08% of the nuclear DNA is occupied by rRNA coding sequences and that the average repetition frequency of these coding sequences is approximately 144. The arrangement of the rRNA genes and their spacer sequences on long strands of purified rDNA was determined by the examination of the structure of rRNA:DNA hybrids in the electron microscope. Long DNA strands contain several gene sets (18S + 26S) with one repeat unit containing the following sequences in the order given: (a) An 18S gene of length 2.12 kb, (b) an internal transcribed spacer of length 2.01 kb, which contains a short sequence that may code for a 5.8S rRNA, (c) A 26S gene of length 4.06 kb which, in 20% of the cases, contains an intron with an average length of 5.62 kb, and (d) an external spacer of average length 9.23 kb.

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The macronuclear ribosomal DNA of Tetrahymena pyriformis is a palindrome

Cited by 228 publications

References 40 publications

Short inverted repeats initiate gene amplification through the formation of a large DNA palindrome in mammalian cells

Short inverted repeats initiate gene amplification through the formation of a large DNA palindrome in mammalian cells

Localization of transcribed regions on extrachromosomal ribosomal RNA genes of Tetrahymena thermophila by R-loop mapping.

Sequence arrangement of the rRNA genes of the dipteran Sarcophaga bullata

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