PIF1: a DNA helicase in yeast mitochondria.

Lahaye, A.; Stahl, Hans; Thinessempoux, D.; Foury, Françoise

doi:10.1002/j.1460-2075.1991.tb08034.x

Cited by 185 publications

(137 citation statements)

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“…During computational identification of DNA repeats, we found that the A. thaliana genome harbors multiple dispersed Ϸ10-kb units that encode two proteins similar to the yeast Pif1p DNA helicase (23)(24) and RPA (25)(26). On the basis of pairwise nucleotide identity, these DNA units can be divided into several groups of 2-10 sequences each.…”

Section: Resultsmentioning

confidence: 99%

Rolling-circle transposons in eukaryotes

Kapitonov

Jurka²

2001

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

456

541

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All eukaryotic DNA transposons reported so far belong to a single category of elements transposed by the so-called ''cut-and-paste'' mechanism. Here, we report a previously unknown category of eukaryotic DNA transposons, Helitron, which transpose by rollingcircle replication. Autonomous Helitrons encode a 5 -to-3 DNA helicase and nuclease͞ligase similar to those encoded by known rolling-circle replicons. Helitron-like transposons have conservative 5 -TC and CTRR-3 termini and do not have terminal inverted repeats. They contain 16-to 20-bp hairpins separated by 10 -12 nucleotides from the 3 -end and transpose precisely between the 5 -A and T-3 , with no modifications of the AT target sites. Together with their multiple diverged nonautonomous descendants, Helitrons constitute Ϸ2% of both the Arabidopsis thaliana and Caenorhabditis elegans genomes and also colonize the Oriza sativa genome. Sequence conservation suggests that Helitrons continue to be transposed.

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Section: Resultsmentioning

confidence: 99%

Rolling-circle transposons in eukaryotes

Kapitonov

Jurka²

2001

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

456

541

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“…It was first identified in the budding yeast Saccharomyces cerevisiae for its role in mitochondrial DNA maintenance as cells lacking Pif1 lose mitochondrial DNA at high rates, generating respiratory-deficient (petite) cells (Foury and Kolodynski 1983;Lahaye et al 1991). Cells also express a nuclear form of Pif1 that has functions independent of mitochondrial DNA maintenance, with its role in telomerase regulation being the most thoroughly characterized.…”

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confidence: 99%

Telomerase Is Essential to Alleviate Pif1-Induced Replication Stress at Telomeres

et al. 2009

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Pif1, an evolutionarily conserved helicase, negatively regulates telomere length by removing telomerase from chromosome ends. Pif1 has also been implicated in DNA replication processes such as Okazaki fragment maturation and replication fork pausing. We find that overexpression of Saccharomyces cervisiae PIF1 results in dose-dependent growth inhibition. Strong overexpression causes relocalization of the DNA damage response factors Rfa1 and Mre11 into nuclear foci and activation of the Rad53 DNA damage checkpoint kinase, indicating that the toxicity is caused by accumulation of DNA damage. We screened the complete set of $4800 haploid gene deletion mutants and found that moderate overexpression of PIF1, which is only mildly toxic on its own, causes growth defects in strains with mutations in genes involved in DNA replication and the DNA damage response. Interestingly, we find that telomerase-deficient strains are also sensitive to PIF1 overexpression. Our data are consistent with a model whereby increased levels of Pif1 interfere with DNA replication, causing collapsed replication forks. At chromosome ends, collapsed forks result in truncated telomeres that must be rapidly elongated by telomerase to maintain viability.

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“…The Ku70/Ku80 heterodimer, while essential for nonhomologous end joining, also plays a key role both in the recruitment of telomerase to the telomere and in the protection of ends from degradation (9,25,65,74). Several DNA helicases and nucleases are also known to play key roles in the replication and maintenance of telomeres, including Pif1, Sgs1, Mre11, Rtel, and others (20,34,41).Pif1 is a member of a 5Ј-to-3Ј DNA helicase family whose other closest members include Rrm3 and, in Schizosaccharomyces pombe, Pfh1 (33,37,77). Unlike Rrm3 and Pif1, Pfh1 is essential (77).…”

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confidence: 99%

“…Pif1 is a member of a 5Ј-to-3Ј DNA helicase family whose other closest members include Rrm3 and, in Schizosaccharomyces pombe, Pfh1 (33,37,77). Unlike Rrm3 and Pif1, Pfh1 is essential (77).…”

mentioning

confidence: 99%

“…Interestingly, ScPif1 (but not Rrm3) colocalizes almost exclusively with Rad52 in nuclei and is recruited to discrete foci after DNA damage (71). ScPif1 and Rrm3 also play roles in the mitochondria, where they contribute to mitochondrial genome stability (21,37,51,52,67,70). Finally, both ScPif1 and Pfh1 interact genetically with the Dna2 helicase and cooperate to ensure the correct processing of Okazaki fragments during DNA replication (17,58).…”

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confidence: 99%

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Murine Pif1 Interacts with Telomerase and Is Dispensable for Telomere Function In Vivo

Snow

Mateyak

Paderova

et al. 2007

Molecular and Cellular Biology

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Pif1 is a 5 -to-3 DNA helicase critical to DNA replication and telomere length maintenance in the budding yeast Saccharomyces cerevisiae. ScPif1 is a negative regulator of telomeric repeat synthesis by telomerase, and recombinant ScPif1 promotes the dissociation of the telomerase RNA template from telomeric DNA in vitro. In order to dissect the role of mPif1 in mammals, we cloned and disrupted the mPif1 gene. In wild-type animals, mPif1 expression was detected only in embryonic and hematopoietic lineages. mPif1 ؊/؊ mice were viable at expected frequencies, displayed no visible abnormalities, and showed no reproducible alteration in telomere length in two different null backgrounds, even after several generations. Spectral karyotyping of mPif1 ؊/؊ fibroblasts and splenocytes revealed no significant change in chromosomal rearrangements. Furthermore, induction of apoptosis or DNA damage revealed no differences in cell viability compared to what was found for wild-type fibroblasts and splenocytes. Despite a novel association of mPif1 with telomerase, mPif1 did not affect the elongation activity of telomerase in vitro. Thus, in contrast to what occurs with ScPif1, murine telomere homeostasis or genetic stability does not depend on mPif1, perhaps due to fundamental differences in the regulation of telomerase and/or telomere length between mice and yeast or due to genetic redundancy with other DNA helicases.Homeostatic telomere length is achieved by a balance between the extension of the 3Ј telomeric repeats by telomerase or by homologous recombination between telomeric tracts and telomere erosion due to incomplete DNA replication or nucleolytic degradation (30). Telomerase acts to lengthen telomeres via the reverse transcription of an RNA template (encoded by TERC in mammals or TLC1 in Saccharomyces cerevisiae) by a telomerase reverse transcriptase (TERT or Est2, respectively) (30). In the absence of telomerase, telomeric repeats can also be maintained via homologous recombination (12). Excessive telomere lengthening is usually curtailed by cis-inhibitory telomere binding factors, such as Rif1 and Rap1 in S. cerevisiae and TRF1 in humans, or by the action of nucleases (30). In particular instances, telomeric tracts undergo saltatory attrition via the excision of telomeric DNA circles, thus preventing unregulated telomere lengthening (12,40,73).This equilibrium is not simply a push and pull between factors that strictly promote or oppose telomere extension. In S. cerevisiae, the trimeric protein complex composed of Cdc13, Stn1, and Ten1 plays a critical role in the protection of chromosome ends from nucleolytic degradation, and the complex serves both positive and negative roles in the access of telomerase to the telomere during late S phase (24,27,66). The Ku70/Ku80 heterodimer, while essential for nonhomologous end joining, also plays a key role both in the recruitment of telomerase to the telomere and in the protection of ends from degradation (9,25,65,74). Several DNA helicases and nucleases are also known to play ...

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PIF1: a DNA helicase in yeast mitochondria.

Cited by 185 publications

References 48 publications

Rolling-circle transposons in eukaryotes

Rolling-circle transposons in eukaryotes

Telomerase Is Essential to Alleviate Pif1-Induced Replication Stress at Telomeres

Murine Pif1 Interacts with Telomerase and Is Dispensable for Telomere Function In Vivo

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