reza saleki - Academia.edu (original) (raw)

Papers by reza saleki

Kidney International, 2000

channel with a single channel characteristics of a highly ubiquitination. The epithelial Na ϩ cha... more channel with a single channel characteristics of a highly ubiquitination. The epithelial Na ϩ channel (ENaC) is com-Na ϩ selective, low conductance (ϳ5 pS) and high amilorprised of three subunits, ␣, ␤ and ␥, and plays an essential role ide sensitivity (Ki ϳ10 to 100 nmol/L) 14]. Each ENaC in Na ϩ and fluid absorption in the kidney, colon and lung.

Current Genetics, 1999

Fission yeast strains auxotrophic for leucine are unable to proliferate in normally supplemented ... more Fission yeast strains auxotrophic for leucine are unable to proliferate in normally supplemented minimal media adjusted to pH 6.4 or above. High-pH sensitivity can be suppressed by the loss of Pub1, an E3 ubiquitin ligase, or by the replacement of NH4+ with a non-repressing source of nitrogen such as L-proline. In this report we show pub1 to be required for the rapid down-regulation of leucine uptake observed in response to the addition of NH4+ to the growth media. Furthermore, we corroborate earlier results demonstrating the transport of leucine to be negatively influenced by high extracellular pH. pub1 is homologous to the budding yeast nitrogen permease inactivator, NPI1/RSP5, which mediates the ubiquitination and subsequent destruction of NH4+-sensitive permeases. The high-pH sensitivity of cells auxotrophic for leucine thus seems to reflect an inability of NH4+-insensitive permeases to transport sufficient leucine under conditions where the proton gradient driving nutrient transport is low, and NH4+-sensitive permeases have been destroyed. Intriguingly, the partial suppression of both high pH sensitivity, and the inactivating effect of NH4+ on leucine transport, seen in pub1-1 point mutants, becomes as complete as seen in pub1Δ backgrounds when cells have concomitantly lost the function of the spc1 stress-activated MAPK.

Three mutant strains of Arabidopsis thaliana var Columbia were selected for their ability to germ... more Three mutant strains of Arabidopsis thaliana var Columbia were selected for their ability to germinate in elevated concentrations of NaCI. They were not more tolerant than wild type at subsequent development stages. Wild-type strains could not germinate at concentrations >125 mM NaCI. l w o of the mutant strains, RS17 and RS20, could withstand up to 225 mM, whereas RS19 was resistant to 175 mM. l h e RS mutants could also germinate under even lower osmotic potentials imposed by high concentrations of exogenous mannitol (550 mM), whereas the effects of elevated levels of KCI, KzS04, and LiCl were similar among the mutants and wild type. Therefore, the mutants are primarily osmotolerant, but they also possess a degree of ionic tolerance for sodium. Sodium and potassium contents of seeds exposed to high salinities indicated that the NaCI-tolerant mutants absorbed more of these respective cations during imbibition. These higher interna1 concentrations of potassium and sodium could contribute to the osmotic adjustment of the germinating seeds to the low osmotic potential of the externa1 medium. Genetic analysis of F, and Fz progeny of outcrosses suggest that the salt-tolerant mutations are recessive and that they define three complementation groups.

Molecular and General Genetics, 1997

A strain of Schizosaccharomyces pombe carrying a disrupted Na+/H+ antiporter gene (sod2::sup3-5),... more A strain of Schizosaccharomyces pombe carrying a disrupted Na+/H+ antiporter gene (sod2::sup3-5), in addition to the common auxotrophic mutations, ade6-216, ura4-D18 and leu1-32, is highly sensitive to media adjusted to pH 6.9. Reversion analysis of this strain yielded a group of revertants capable of growth at pH 6.9. Two of the revertants elongated and failed to form colonies at pH 3.5. Genetic characterization of one of the pH-sensitive elongated strains, J227, showed the presence of two independently segregating mutations. One, pub1 ( protein ubiquitin ligase 1), has recently been reported as an E3 protein ubiquitin ligase involved in cdc25 turnover. The second has been named elp3-1 (elongated at low pH). Genetic dissection of the original strain revealed that poor growth at high pH was due to the presence of the auxotrophic markers, suggesting a possible inhibitory effect of high pH on the function of permeases responsible for uptake of the necessary nutrients. Suppression of the high pH sensitivity required the presence of both the pub1-1 and elp3-1 mutations. While the pub1-1 mutation reduced the capacity of cells to tolerate relatively moderate concentrations of LiCl (3 mM) in liquid culture, it was capable of partially suppressing the extreme Li+ sensitivity caused by the sod2 disruption. Under these conditions, the growth of pub1-1 sod2::ura4 double mutant cells was improved over that of either pub1-1 or sod2::ura4 cells. The elp3-1 mutation had no effect on the Li+ tolerance in either wild-type or sod2::ura4 backgrounds. pub1-1 cells are elongated and incapable of colony formation at pH 3.5. In contrast, elp3-1 cells are elongated at pH 3.5 and pH␣5.5 (the normal pH of minimal medium) but can form colonies under both conditions. J227 cells are significantly longer than either single mutant at pH 3.5 and do not form colonies but are visually similar to elp3-1 cells at pH 5.5. Complementation cloning in the J227 background yielded a genomic clone of pub1, allowing us to define the intron-exon structure of the gene. Sequences with high homology to the predicted amino acid sequence of pub1 have been identified in Saccharomyces cerevisiae (RSP5/NPI1), human (hRPF1), mouse (mNedd4), and rat (rNedd4). Based on the nature of our mutant selection, the pH-sensitive phenotype of the strains selected, and the known involvement of RSP5/NPI1 in membrane permease turnover in S. cerevisiae, we hypothesize a role for pub1, either directly or indirectly, in regulating membrane transport processes. This is further supported by the broad range of effects that the pub1-1 mutation exerts on overall performance of cells at high and low external pH, and in the presence of toxic levels of Li+.

Cytogenetic and Genome Research, 2003

... External Resources 7. Devriendt K, Petit P, Matthijs G, Vermeesch JR, Holvoet M, De Muelenaer... more ... External Resources 7. Devriendt K, Petit P, Matthijs G, Vermeesch JR, Holvoet M, De Muelenaere A, Marynen P, Cassiman JJ, Fryns JP ... Reddy KS, Parsons L, Colman L: Jumping translocations involving chromosome 1q in a patient with Crohn disease and acute monocytic ...

Cytogenetic and Genome Research, 2003

Kidney International, 2000

Current Genetics, 1999

Molecular and General Genetics, 1997

Cytogenetic and Genome Research, 2003