A Dicer-like protein in <i>Tetrahymena</i> has distinct functions in genome rearrangement, chromosome segregation, and meiotic prophase

Mochizuki, Kazufumi; Gorovsky, Martin A.

doi:10.1101/gad.1265105

Cited by 205 publications

(259 citation statements)

References 53 publications

(87 reference statements)

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“…2C, top panel). The abnormal accumulation of the 23-24 nt small RNAs in conjugating Dcl1 (À/À) cells has been previously reported (Malone et al 2005;Mochizuki and Gorovsky 2005), but until now their identity was obscure, as they do not crossreact with well-established scnRNAs, such as M-related scnRNAs (Fig. 2C, bottom panel).…”

Section: Resultsmentioning

confidence: 96%

Dicer independent small RNAs associate with telomeric heterochromatin

Cao¹,

Li²,

Hiew³

et al. 2009

RNA

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Small RNAs play important roles in the establishment and maintenance of heterochromatin structures. We show the presence of telomere specific small RNAs (tel-sRNAs) in mouse embryonic stem cells that are ;24 nucleotides in length, Dicer-independent, and 29-O-methylated at the 39 terminus. The tel-sRNAs are asymmetric with specificity toward telomere G-rich strand, and evolutionarily conserved from protozoan to mammalian cells. Furthermore, tel-sRNAs are up-regulated in cells that carry null mutation of H3K4 methyltransferase MLL (Mll (À/À) ) and down-regulated in cells that carry null mutations of histone H3K9 methyltransferase SUV39H (Suv39h1/h2 (À/À) ), suggesting that they are subject to epigenetic regulation. These results support that tel-sRNAs are heterochromatin associated pi-like small RNAs.

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Section: Resultsmentioning

confidence: 96%

Dicer independent small RNAs associate with telomeric heterochromatin

Cao¹,

Li²,

Hiew³

et al. 2009

RNA

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“…This overall organization is maintained in Dicer-like proteins from animals (H. sapiens), fungi (Schyzosaccharomyces pombe), and plants (A. thaliana) (Figure 1) with the greatest variability associated with the presence or absence of the DSRM and/or of the PAZ domains. In Tetrahymena thermophila there are three Dicer-like sequences: Dcr2, which contains only the helicase and the two RNaseIII domains (Figure 1), and Dcr1 and Dcl1, which are more divergent (Lee and Collins 2006;Mochizuki and Gorovsky 2005). Indeed, Dcl1 only includes the RNaseIII motifs and a C-terminal DSRM.…”

Section: Phytophthora Infestansmentioning

confidence: 99%

“…RNAi has also been implicated in the programmed excision of excess DNA in ciliated protozoa such as T. thermophila and P. tetraurelia (Garnier et al 2004;Mochizuki and Gorovsky 2005;Nowacki et al 2005;Yao and Chao 2005). This process requires small RNAs, termed scan RNAs, and components of the RNA machinery that direct H3K9 methylation of the chromatin associated with the sequences to be deleted (Garnier et al 2004;Liu et al 2004b;Mochizuki and Gorovsky 2005;Yao and Chao 2005).…”

Section: Additional (Derived?) Functions Of the Rnai Machinerymentioning

confidence: 99%

“…This process requires small RNAs, termed scan RNAs, and components of the RNA machinery that direct H3K9 methylation of the chromatin associated with the sequences to be deleted (Garnier et al 2004;Liu et al 2004b;Mochizuki and Gorovsky 2005;Yao and Chao 2005). Many of the eliminated sequences appear to be derived from transposons (Lee and Collins 2006;Yao and Chao 2005) and RNA-mediated DNA elimination may have evolved as an extension of the role of the RNAi machinery in the transcriptional silencing of transposon/repetitive sequences.…”

Section: Additional (Derived?) Functions Of the Rnai Machinerymentioning

confidence: 99%

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On the origin and functions of RNA-mediated silencing: from protists to man

2006

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Double-stranded RNA has been shown to induce gene silencing in diverse eukaryotes and by a variety of pathways. We have examined the taxonomic distribution and the phylogenetic relationship of key components of the RNA interference (RNAi) machinery in members of five eukaryotic supergroups. On the basis of the parsimony principle, our analyses suggest that a relatively complex RNAi machinery was already present in the last common ancestor of eukaryotes and consisted, at a minimum, of one Argonautelike polypeptide, one Piwi-like protein, one Dicer, and one RNAdependent RNA polymerase. As proposed before, the ancestral (but non-essential) role of these components may have been in defense responses against genomic parasites such as transposable elements and viruses. From a mechanistic perspective, the RNAi machinery in the eukaryotic ancestor may have been capable of both small-RNA-guided transcript degradation as well as transcriptional repression, most likely through histone modifications. Both roles appear to be widespread among living eukaryotes and this diversification of function could account for the evolutionary conservation of duplicated Argonaute-Piwi proteins. In contrast, additional RNAi-mediated pathways such as RNA-directed DNA methylation, programmed genome rearrangements, meiotic silencing by unpaired DNA, and miRNA-mediated gene regulation may have evolved independently in specific lineages.

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“…During DNA elimination in Tetrahymena, bidirectional micronuclear transcripts containing IESs (7) are processed by a dicer-like protein, Dcl1p, into small interfering RNA-like ϳ28-nucleotide scan RNAs (scnRNAs) (25). scnRNAs are associated with Twi1p, an Argonaute protein (23), which is required for DNA elimination (22).…”

Section: Characterization Of Thementioning

confidence: 99%

Centromeric Histone H3 Is Essential for Vegetative Cell Division and for DNA Elimination during Conjugation in Tetrahymena thermophila

Cui

Gorovsky

2006

Molecular and Cellular Biology

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The Tetrahymena thermophila CNA1 gene encodes the centromeric H3, Cna1p. Green fluorescent protein (GFP)-tagged Cna1p localizes in micronuclei in dots whose number and behavior during mitosis and conjugation are consistent with centromeres. During interphase, Cna1p-GFP localizes in peripheral dots, suggesting centromeres are associated with the nuclear envelope. Newly synthesized Cna1p-GFP enters micronuclei in mitosis and accumulates in the nucleoplasm. Its deposition at centromeres starts at early S phase and continues through most of S phase. CNA1 is required for vegetative cell growth. Knockdown of CNA1 genes in the somatic macronucleus results in micronuclear DNA loss and delayed chromosome segregation during mitosis. During conjugation, Cna1p-GFP disappears from the centromeres in the developing macronucleus, consistent with centromeric sequences being internal eliminated sequences. Surprisingly, zygotic CNA1 is required for efficient elimination of germ line-specific sequences during development of the new macronuclei but not for the RNA interference pathway, through which sequences are targeted for elimination. Zygotically expressed Cna1p localizes in the spherical structures in which the later stages of DNA elimination occur, and these structures cannot be formed in the absence of zygotic CNA1, suggesting that, in addition to functioning in centromeres, Cna1p may also play a role in organizing the formation of the DNA elimination structures.

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A Dicer-like protein in Tetrahymena has distinct functions in genome rearrangement, chromosome segregation, and meiotic prophase

Cited by 205 publications

References 53 publications

Dicer independent small RNAs associate with telomeric heterochromatin

Dicer independent small RNAs associate with telomeric heterochromatin

On the origin and functions of RNA-mediated silencing: from protists to man

Centromeric Histone H3 Is Essential for Vegetative Cell Division and for DNA Elimination during Conjugation in Tetrahymena thermophila

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