Internal sequences are eliminated from genes during macronuclear development in the ciliated protozoan oxytricha nova

Abstract In the hypotrichous ciliated protozoan Oxytricha nova, approximately 95% of the micronuclear genome, including all of the repetitive DNA and most of the unique sequence DNA, is eliminated during the formation of the macronuclear genome. We have examined the interspersion patterns of repetitive and unique and eliminated and retained sequences in the micronuclear genome by characterizing randomly selected clones of micronuclear DNA. Three major classes of clones have been defined: (1) those containing primarily unique, retained sequences; (2) those containing only unique, eliminated sequences; and (3) those containing only repetitive, eliminated sequences. Clones of type one and three document two aspects of organization observed previously: clustering of macronuclear destined sequences and the presence of a prevalent repetitive element. Clones of the second type demonstrate for the first time that eliminated unique sequence DNA occurs in long stretches uninterrupted by repetitive sequences. To further examine repetitive sequence interspersion, we characterized the repetitive sequence family that is present in 50% of the clones (class three above). A consensus map of this element was obtained by mapping approximately 80 phage clones and by hybridization to digests of micronuclear DNA. The repeat element is extremely large (approximately 24 kb) and is interspersed with both macronuclear destined sequences and eliminated unique sequences.

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Nucleic acid splicing events occur frequently during macronuclear development in the protozoan Oxytricha nova and involve the elimination of unique DNA.

Genes & Development ◽

10.1101/gad.1.4.323 ◽

1987 ◽

Vol 1 (4) ◽

pp. 323-336 ◽

Cited By ~ 30

Author(s):

R M Ribas-Aparicio ◽

J J Sparkowski ◽

A E Proulx ◽

J D Mitchell ◽

L A Klobutcher

Keyword(s):

Nucleic Acid ◽

Macronuclear Development ◽

Oxytricha Nova

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Polytene chromosomes of Oxytricha: Biochemical and morphological changes during macronuclear development in a ciliated protozoan

Chromosoma ◽

10.1007/bf00331828 ◽

1976 ◽

Vol 54 (1) ◽

pp. 1-13 ◽

Cited By ~ 34

Author(s):

Brian B. Spear ◽

Marlene R. Lauth

Keyword(s):

Morphological Changes ◽

Polytene Chromosomes ◽

Ciliated Protozoan ◽

Macronuclear Development

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Role of Micronucleus-Limited DNA in Programmed Deletion of mse2.9 during Macronuclear Development of Tetrahymena thermophila

Eukaryotic Cell ◽

10.1128/ec.3.2.288-301.2004 ◽

2004 ◽

Vol 3 (2) ◽

pp. 288-301 ◽

Cited By ~ 6

Author(s):

Jeffrey S. Fillingham ◽

Ronald E. Pearlman

Keyword(s):

Epigenetic Regulation ◽

Tetrahymena Thermophila ◽

Germ Line ◽

Sexual Cycle ◽

Ciliated Protozoan ◽

Dna Rearrangements ◽

Macronuclear Development ◽

Dna Deletion

ABSTRACT Extensive programmed DNA rearrangements occur during the development of the somatic macronucleus from the germ line micronucleus in the sexual cycle of the ciliated protozoan Tetrahymena thermophila. Using an in vivo processing assay, we analyzed the role of micronucleus-limited DNA during the programmed deletion of mse2.9, an internal eliminated sequence (IES). We identified a 200-bp region within mse2.9 that contains an important cis-acting element which is required for the targeting of efficient programmed deletion. Our results, obtained with a series of mse2.9-based chimeric IESs, led us to suggest that the cis-acting elements in both micronucleus-limited and macronucleus-retained flanking DNAs stimulate programmed deletion to different degrees depending on the particular eliminated sequence. The mse2.9 IES is situated within the second intron of the micronuclear locus of the ARP1 gene. We show that the expression of ARP1 is not essential for the growth of Tetrahymena. Our results also suggest that mse2.9 is not subject to epigenetic regulation of DNA deletion, placing possible constraints on the scan RNA model of IES excision.

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Inverted terminal repeats are added to genes during macronuclear development in Oxytricha nova.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.79.10.3255 ◽

1982 ◽

Vol 79 (10) ◽

pp. 3255-3259 ◽

Cited By ~ 30

Author(s):

R. E. Boswell ◽

L. A. Klobutcher ◽

D. M. Prescott

Keyword(s):

Macronuclear Development ◽

Inverted Terminal Repeats ◽

Terminal Repeats ◽

Oxytricha Nova

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Seasonal cycle of the ciliated protozoan and micrometazoan biomass in a Gulf of Maine estuary

Estuarine Coastal and Shelf Science ◽

10.1016/0272-7714(87)90116-8 ◽

1987 ◽

Vol 25 (5) ◽

pp. 581-598 ◽

Cited By ~ 24

Author(s):

Noelia Revelante ◽

Malvern Gilmartin

Keyword(s):

Seasonal Cycle ◽

Gulf Of Maine ◽

Ciliated Protozoan

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Ciliary protein conservation during development in the ciliated protozoan, Oxytricha.

The Journal of Cell Biology ◽

10.1083/jcb.105.6.2855 ◽

1987 ◽

Vol 105 (6) ◽

pp. 2855-2859 ◽

Cited By ~ 7

Author(s):

G W Grimes ◽

R H Gavin

Keyword(s):

Cell Division ◽

Daughter Cell ◽

Basal Bodies ◽

Ciliated Protozoan ◽

Subunit Exchange ◽

Electrophoretic Data ◽

Autoradiographic Analysis ◽

Protein Conservation ◽

The One ◽

Molecular Conservation

The ciliated protozoan Oxytricha fallax possesses multiple highly localized clusters of basal bodies and cilia, all of which are broken down and rebuilt during prefission morphogenesis-with one major exception. The adoral zone of membranelles (AZM) of the ciliate oral apparatus contains approximately 1,500-2,000 basal bodies and cilia, and it is the only compound ciliary structure that is passed morphologically intact to one daughter cell at each cell division. By labeling all proteins in cells, and then picking the one daughter cell possessing the original labeled AZM, we could then evaluate whether or not the ciliary proteins of the AZM were diluted (i.e., either by degradation to constituent amino acids or by subunit exchange) during cell division. Autoradiographic analysis demonstrated that the label was highly conserved in the AZM (i.e., we saw no evidence of turnover), and electrophoretic data illustrate that at least one of the proteins of the AZM is tubulin. We, therefore, conclude that for at least some of the ciliary and basal body proteins of Oxytricha fallax, AZM morphological conservation is essentially equivalent to molecular conservation.

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