The Condensin Complex Is Essential for Amitotic Segregation of Bulk Chromosomes, but Not Nucleoli, in the Ciliate <i>Tetrahymena thermophila</i>

Cervantes, Marcella D.; Coyne, Robert S.; Xi, Xiaohui; Yao, Meng-Chao

doi:10.1128/mcb.02315-05

Cited by 26 publications

(19 citation statements)

References 53 publications

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“…Somatic gene knockdown of SMC4 causes defects in amitotic division of the macronucleus, thereby compromising vegetative growth of T. thermophila (Cervantes et al 2006). Notably, the T. thermophila genome possesses multiple genes for CAP-D2 and CAP-H, a situation rarely found in other eukaryotic genomes.…”

Section: Tetrahymena Thermophilamentioning

confidence: 99%

Condensins: universal organizers of chromosomes with diverse functions

2012

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Condensins are multisubunit protein complexes that play a fundamental role in the structural and functional organization of chromosomes in the three domains of life. Most eukaryotic species have two different types of condensin complexes, known as condensins I and II, that fulfill nonoverlapping functions and are subjected to differential regulation during mitosis and meiosis. Recent studies revealed that the two complexes contribute to a wide variety of interphase chromosome functions, such as gene regulation, recombination, and repair. Also emerging are their cell type- and tissue-specific functions and relevance to human disease. Biochemical and structural analyses of eukaryotic and bacterial condensins steadily uncover the mechanisms of action of this class of highly sophisticated molecular machines. Future studies on condensins will not only enhance our understanding of chromosome architecture and dynamics, but also help address a previously underappreciated yet profound set of questions in chromosome biology.

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Section: Tetrahymena Thermophilamentioning

confidence: 99%

Condensins: universal organizers of chromosomes with diverse functions

2012

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“…Tetrahymena cells multiply through binary fission, typically in axenic peptone medium in the laboratory. During this vegetative growth phase, the micronucleus divides by mitosis, but the macronucleus divides by amitosis, an unusual division process without apparent chromosome condensation or spindle formation (7). RNA transcription occurs exclusively in the macronucleus, whereas the micronucleus remains condensed and silent throughout this phase.…”

Section: Tetrahymena Life Cyclementioning

confidence: 99%

Programmed Genome Rearrangements in Tetrahymena

2014

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Ciliates are champions in programmed genome rearrangements. They carry out extensive restructuring during differentiation to drastically alter the complexity, relative copy number, and arrangement of sequences in the somatic genome. This chapter focuses on the model ciliate Tetrahymena, perhaps the simplest and best-understood ciliate studied. It summarizes past studies on various genome rearrangement processes and describes in detail the remarkable progress made in the past decade on the understanding of DNA deletion and other processes. The process occurs at thousands of specific sites to remove defined DNA segments that comprise roughly one-third of the genome including all transposons. Interestingly, this DNA rearranging process is a special form of RNA interference. It involves the production of double-stranded RNA and small RNA that guides the formation of heterochromatin. A domesticated piggyBac transposase is believed to cut off the marked chromatin, and the retained sequences are joined together through nonhomologous end-joining processes. Many of the proteins and DNA players involved have been analyzed and are described. This link provides possible explanations for the evolution, mechanism, and functional roles of the process. The article also discusses the interactions between parental and progeny somatic nuclei that affect the selection of sequences for deletion, and how the specific deletion boundaries are determined after heterochromatin marking.

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“…Changes in gene copy number resulting from chromosome aberrations would represent a smaller proportional alteration in gene dosage in a polyploid compared with a diploid cell. Indeed, the highly polyploid macronuclei of ciliates divide amitotically, without accurate segregation of sister chromatids (Cervantes et al 2006).…”

Section: Polyploidy and Mitotic Fidelitymentioning

confidence: 99%

Error-prone polyploid mitosis during normal Drosophila development

Fox¹,

Gall²,

Spradling³

2010

Genes Dev.

152

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Endopolyploidy arises during normal development in many species when cells undergo endocycles-variant cell cycles in which DNA replicates but daughter cells do not form. Normally, polyploid cells do not divide mitotically after initiating endocycles; hence, little is known about their mitotic competence. However, polyploid cells are found in many tumors, and the enhanced chromosomal instability of polyploid cells in culture suggests that such cells contribute to tumor aneuploidy. Here, we describe a novel polyploid Drosophila cell type that undergoes normal mitotic cycles as part of a remodeling process that forms the adult rectal papillae. Similar polyploid mitotic divisions, but not depolyploidizing divisions, were observed during adult ileum development in the mosquito Culex pipiens. Extended anaphases, chromosome bridges, and lagging chromosomes were frequent during these polyploid divisions, despite normal expression of cell cycle regulators. Our results show that the switch to endocycles during development is not irreversible, but argue that the polyploid mitotic cycle is inherently error-prone, and that polyploid mitoses may help destabilize the cancer genome.[Keywords: Polyploidy; endocycle; chromosomal instability; hindgut; Drosophila] Supplemental material is available at http://www.genesdev.org.

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The Condensin Complex Is Essential for Amitotic Segregation of Bulk Chromosomes, but Not Nucleoli, in the Ciliate Tetrahymena thermophila

Cited by 26 publications

References 53 publications

Condensins: universal organizers of chromosomes with diverse functions

Condensins: universal organizers of chromosomes with diverse functions

Programmed Genome Rearrangements in Tetrahymena

Error-prone polyploid mitosis during normal Drosophila development

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