Cell Division Defects of
            <i>Schizosaccharomyces pombe liz1</i>
            <sup>−</sup>
            Mutants Are Caused by Defects in Pantothenate Uptake

Stolz, Jürgen; Caspari, Thomas; Carr, Antony; Sauer, Norbert

doi:10.1128/ec.3.2.406-412.2004

Cited by 22 publications

(30 citation statements)

References 42 publications

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“…These findings suggest that in response to HU, ⌬tor1 cells are arrested with 1C nuclei content but cytokinesis of the previous cell cycle is delayed. A similar delay in septation in the presence of HU has been reported for mutants lacking Liz1, a pantothenate transporter (37, 53); this delay results from an indirect effect of HU on pantothenate biosynthesis (53). Unlike the case with ⌬liz1 mutants, addition of pantothenate to the medium did not rescue the HU sensitivity of ⌬tor1 mutants (data not shown); thus, the aberrant response to HU in ⌬tor1 mutants occurs via a distinct mechanism.…”

Section: Tor1mentioning

confidence: 58%

TOR Complex 2 Controls Gene Silencing, Telomere Length Maintenance, and Survival under DNA-Damaging Conditions

Schonbrun

Laor

López‐Maury

et al. 2009

Molecular and Cellular Biology

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The Target Of Rapamycin (TOR) kinase belongs to the highly conserved eukaryotic family of phosphatidylinositol-3-kinase-related kinases (PIKKs). TOR proteins are found at the core of two distinct evolutionarily conserved complexes, TORC1 and TORC2. Disruption of TORC1 or TORC2 results in characteristically dissimilar phenotypes. TORC1 is a major cell growth regulator, while the cellular roles of TORC2 are not well understood. In the fission yeast Schizosaccharomyces pombe, Tor1 is a component of the TORC2 complex, which is particularly required during starvation and various stress conditions. Our genome-wide gene expression analysis of ⌬tor1 mutants indicates an extensive similarity with chromatin structure mutants. Consistently, TORC2 regulates several chromatin-mediated functions, including gene silencing, telomere length maintenance, and tolerance to DNA damage. These novel cellular roles of TORC2 are rapamycin insensitive. Cells lacking Tor1 are highly sensitive to the DNA-damaging drugs hydroxyurea (HU) and methyl methanesulfonate, similar to mutants of the checkpoint kinase Rad3 (ATR). Unlike Rad3, Tor1 is not required for the cell cycle arrest in the presence of damaged DNA. Instead, Tor1 becomes essential for dephosphorylation and reactivation of the cyclin-dependent kinase Cdc2, thus allowing reentry into mitosis following recovery from DNA replication arrest. Taken together, our data highlight critical roles for TORC2 in chromatin metabolism and in promoting mitotic entry, most notably after recovery from DNA-damaging conditions. These data place TOR proteins in line with other PIKK members, such as ATM and ATR, as guardians of genome stability.

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Section: Tor1mentioning

confidence: 58%

TOR Complex 2 Controls Gene Silencing, Telomere Length Maintenance, and Survival under DNA-Damaging Conditions

Schonbrun

Laor

López‐Maury

et al. 2009

Molecular and Cellular Biology

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“…The PCR product was ligated into the NotI site of a modified pUC19 plasmid and cut at the two remaining EcoRI sites to remove 723 bp from the bsu1 ϩ coding region. Next, ura4 ϩ was integrated as an EcoRI fragment from pIC20R-ura4 ϩ (37). In the final plasmid, ura4 ϩ was flanked by 126 bp from the 5Ј end and 611 bp from the 3Ј end of bsu1 ϩ .…”

Section: Methodsmentioning

confidence: 99%

Amiloride Uptake and Toxicity in Fission Yeast Are Caused by the Pyridoxine Transporter Encoded by bsu1 ⁺ ( car1 ⁺ )

2005

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Amiloride, a diuretic drug that acts by inhibition of various sodium transporters, is toxic to the fission yeast Schizosaccharomyces pombe. Previous work has established that amiloride sensitivity is caused by expression of car1 ؉ , which encodes a protein with similarity to plasma membrane drug/proton antiporters from the multidrug resistance family. Here we isolated car1؉ by complementation of Saccharomyces cerevisiae mutants that are deficient in pyridoxine biosynthesis and uptake. Our data show that Car1p represents a new high-affinity, plasma membrane-localized import carrier for pyridoxine, pyridoxal, and pyridoxamine. We therefore propose the gene name bsu1 ؉ (for vitamin B 6 uptake) to replace car1 ؉ . Bsu1p displays an acidic pH optimum and is inhibited by various protonophores, demonstrating that the protein works as a proton symporter. The expression of bsu1 ؉ is associated with amiloride sensitivity and pyridoxine uptake in both S. cerevisiae and S. pombe cells. Moreover, amiloride acts as a competitor of pyridoxine uptake, demonstrating that both compounds are substrates of Bsu1p. Taken together, our data show that S. pombe and S. cerevisiae possess unrelated plasma membrane pyridoxine transporters. The S. pombe protein may be structurally related to the unknown human pyridoxine transporter, which is also inhibited by amiloride.Vitamin B 6 is a generic term describing a group of three water-soluble vitamins, pyridoxine (PN), pyridoxal (PL), and pyridoxamine (PM), and the 5Ј-phosphates derived therefrom. Vitamin B 6 is synthesized in plants and most microorganisms but cannot be produced by mammals and thus represents an essential component of the human diet.Vitamin B 6 has a central role in the metabolism of amino acids. PL phosphate (PLP) is the cofactor of amino acid transaminases and decarboxylases and enzymes involved in elimination and replacement reactions (19). A more recently discovered function of vitamin B 6 is protection from reactive oxygen species: PN and PLP are as effective as the well-established antioxidant vitamins C and E in quenching singlet oxygen species (6, 10). Moreover, vitamin B 6 is an intermediate in the synthesis of thiamine (vitamin B 1 ). This metabolic pathway is best known for S. cerevisiae cells, where the pyrimidine moiety of thiamine derives from histidine and PN (reference 49 and references therein). The S. cerevisiae THI5 and THI20 gene families are involved in this pathway (44), and both families have orthologues in many other yeast species. Thus, the yeast thiamine biosynthetic pathway is different from the pathway found in many prokaryotes, where PN is not used as a precursor (43). In addition to having evolved different strategies to synthesize the pyrimidine unit of thiamine, synthesis of the thiazole moiety also follows different routes in pro-and eukaryotes (43).To date, two different pathways for PN biosynthesis have been described. The two pathways differ in the origin of the ring nitrogen of PN that is derived from the amide group of glutamine in S. cer...

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“…Similar transporters were also identified in Schizosaccharomyces pombe. SpLIZ1 was shown to encode a transporter for pantothenate (16) and SpVHT1 to be the homolog of the bakers' yeast vitamin transporter gene VHT1 (17).…”

Section: From the Molekulare Pflanzenphysiologie Friedrich-alexandermentioning

confidence: 99%

Vhr1p, a New Transcription Factor from Budding Yeast, Regulates Biotin-dependent Expression of VHT1 and BIO5

Weider

Machnik

Klebl

et al. 2006

Journal of Biological Chemistry

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Transcription of the Saccharomyces cerevisiae vitamin H transporter gene VHT1 is enhanced by low extracellular biotin. Here we present the identification and characterization of Vhr1p as a transcriptional regulator of VHT1 (VHR1 (YIL056w); VHT1 regulator 1) and the identification of the cis-regulatory target sequences for Vhr1p in two yeast promoters. VHR1 was identified in a complementation screening of mutagenized yeast cells that had lost the capacity to express the gene of the green fluorescent protein (GFP) from the VHT1 promoter. ⌬vhr1 deletion mutants fail to induce VHT1 on low biotin concentrations. In yeast one-hybrid analyses performed with fusions of Vhr1p N-terminal and C-terminal fragments to the Gal4p activation domain or to the Gal4p DNA-binding domain, the Vhr1p N terminus mediated biotin-dependent DNA binding, and the Vhr1p C terminus triggered biotin-dependent transcriptional activation. The analyzed Vhr1p N-terminal fragment has previously been described as a domain of unknown function (DUF352). Deletion and linker scanning analyses of the VHT1 promoter revealed the palindromic 18-nucleotide sequence AATCA-N 8 -TGAYT as the vitamin H-responsive element. This sequence was identified also in the BIO5 promoter that is also transcriptionally activated on low biotin concentrations. Bio5p mediates the transport of 7-keto-8-aminopelargonic acid across the yeast plasma membrane, a compound that is used as a precursor in biotin biosynthesis. ⌬vhr1 deletion mutants fail to induce BIO5 on low biotin concentrations. The presented data characterize Vhr1p as an essential component of the biotin-dependent signal transduction cascade in yeast.

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Cell Division Defects of Schizosaccharomyces pombe liz1 ⁻ Mutants Are Caused by Defects in Pantothenate Uptake

Cited by 22 publications

References 42 publications

TOR Complex 2 Controls Gene Silencing, Telomere Length Maintenance, and Survival under DNA-Damaging Conditions

TOR Complex 2 Controls Gene Silencing, Telomere Length Maintenance, and Survival under DNA-Damaging Conditions

Amiloride Uptake and Toxicity in Fission Yeast Are Caused by the Pyridoxine Transporter Encoded by bsu1 ⁺ ( car1 ⁺ )

Vhr1p, a New Transcription Factor from Budding Yeast, Regulates Biotin-dependent Expression of VHT1 and BIO5

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Cell Division Defects of Schizosaccharomyces pombe liz1 − Mutants Are Caused by Defects in Pantothenate Uptake

Cited by 22 publications

References 42 publications

TOR Complex 2 Controls Gene Silencing, Telomere Length Maintenance, and Survival under DNA-Damaging Conditions

TOR Complex 2 Controls Gene Silencing, Telomere Length Maintenance, and Survival under DNA-Damaging Conditions

Amiloride Uptake and Toxicity in Fission Yeast Are Caused by the Pyridoxine Transporter Encoded by bsu1 + ( car1 + )

Vhr1p, a New Transcription Factor from Budding Yeast, Regulates Biotin-dependent Expression of VHT1 and BIO5

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Cell Division Defects of Schizosaccharomyces pombe liz1 ⁻ Mutants Are Caused by Defects in Pantothenate Uptake

Amiloride Uptake and Toxicity in Fission Yeast Are Caused by the Pyridoxine Transporter Encoded by bsu1 ⁺ ( car1 ⁺ )