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Background: The Saccharomyces Mre11p, Rad50p, and Xrs2p proteins form a complex, called the MRX complex, that is required to maintain telomere length. Cells lacking any one of the three MRX proteins and Mec1p, an ATM-like protein kinase, undergo telomere shortening and ultimately die, phenotypes characteristic of cells lacking telomerase. The other ATM-like yeast kinase, Tel1p, appears to act in the same pathway as MRX: mec1 tel1 cells have telomere phenotypes similar to those of telomerase-deficient cells, whereas the phenotypes of tel1 cells are not exacerbated by the loss of a MRX protein. Results: The nuclease activity of Mre11p was found to be dispensable for the telomerase-promoting activity of the MRX complex. The association of the single-stranded TG 1–3 DNA binding protein Cdc13p with yeast telomeres occurred efficiently in the absence of Tel1p, Mre11p, Rad50p, or Xrs2p. Targeting of catalytically active telomerase to the telomere suppressed the senescence phenotype of mec1 mrx or mec1 tel1 cells. Moreover, when telomerase was targeted to telomeres, telomere lengthening was robust in mec1 mrx and mec1 tel1 cells. Conclusions: These data rule out models in which the MRX complex is necessary for Cdc13p binding to telomeres or in which the MRX complex is necessary for the catalytic activity of telomerase. Rather, the data suggest that the MRX complex is involved in recruiting telomerase activity to yeast telomeres.

We study the critical properties of one-dimensional electron systems with the $1/r^{\alpha}$-type long-range interaction ($\alpha \ge 1$). Using bosonization methods, we discuss how the 1D system exhibits a crossover from the Tomonaga-Luttinger liquid to the Wigner crystal when $\alpha \to 1$. In particular, a detailed analysis is given to the Fermi-edge singularity phenomena when a {\it mobile} core hole is created suddenly in the valence band. It is found that the effect due to the core-hole motion on the Fermi-edge singularity is gradually suppressed as the system approaches the Wigner crystal, and its critical behavior is dominated by the ordinary impurity forward-scattering inherent in a static hole., Comment: 6 pages, submitted to J. Phys. Soc. Jpn

We have previously shown that the RAD50, RAD52, MRE11, XRS2, and HDF1 genes of Saccharomyces cervisiae are involved in the formation of deletions by illegitimate recombination on a monocentric plasmid. In this study, we investigated the effects of mutations of these genes on formation of deletions of a dicentric plasmid, in which DNA double-strand breaks are expected to occur frequently because the two centromeres are pulled to opposite poles in mitosis. We transformed yeast cells with a dicentric plasmid, and after incubation for a few division cycles, cells carrying deleted plasmids were detected using negative selection markers. Deletions occurred at a higher frequency than on the monocentric plasmid and there were short regions of homology at the recombination junctions as observed on the monocentric plasmid. In rad50, mre11, xrs2, and hdf1 mutants, the frequency of occurrence of deletions was reduced by about 50-fold, while in the rad52 mutant, it was comparable to that in the wild-type strain. The end-joining functions of Rad50, Mre11, Xrs2, and Hdf1, suggest that these proteins play important roles in the joining of DNA ends produced on the dicentric plasmid during mitosis.

To examine the mechanism of illegitimate recombination in Saccharomyces cerevisiae, we have developed a plasmid system for quantitative analysis of deletion formation. A can1 cyh2 cell carrying two negative selection markers, the CAN1 and CYH2 genes, on a YCp plasmid is sensitive to canavanine and cycloheximide, but the cell becomes resistant to both drugs when the plasmid has a deletion over the CAN1 and CYH2 genes. Structural analysis of the recombinant plasmids obtained from the resistant cells showed that the plasmids had deletions at various sites of the CAN1-CYH2 region and there were only short regions of homology (1-5 bp) at the recombination junctions. The results indicated that the deletion detected in this system were formed by illegitimate recombination. Study on the effect of several rad mutations showed that the recombination rate was reduced by 30-, 10-, 10-, and 10-fold in the rad52, rad50, mre11, and xrs2 mutants, respectively, while in the rud51, 54, 55, and 57 mutants, the rate was comparable to that in the wild-type strain. The rad52 mutation did not affect length of homology at junction sites of illegitimate recombination.

We study the one–dimensional SU(4) spin–orbital model by means of the abelian bosonization as well as the Lanczos and the density matrix renormalization group methods. Starting from the SU(4) gapless model, we introduce the SU(2) Heisenberg-type perturbations for the spin and the orbital degrees of freedom. We investigate how the orbital gap and/or the spin gap are generated by these perturbations. We find the novel phases which have gapless spin (or orbital) excitations in addition to the known phases with both excitations being gapful or gapless.

Statins have pleiotropic effects, such as improvement in endothelial function and antiinflammatory, antiproliferative, and antioxidative effects, that should be beneficial for patients with chronic heart failure (CHF). The aim of this study was to investigate the long-term effect of statins on neurohumoral activation and cardiac function in patients with CHF.We enrolled 38 outpatients with mild to moderate CHF and radionuclide left ventricular ejection fraction (LVEF)40%. These patients were randomly assigned to receive atorvastatin (10 mg/d) or conventional treatment for heart failure and were prospectively followed up for at least 3 years. At entry, we measured plasma concentrations of brain natriuretic peptides (BNPs) and left ventricular end-diastolic dimension and LVEF by echocardiography; thereafter, these measurements were repeated at least every 6 months. The primary end point was defined as the improvement in cardiac function and BNP.There were no significant differences in age, sex, New York Heart Association class, left ventricular end-diastolic dimension, LVEF, and serum cholesterol level at entry between patients with (n = 19) and without atorvastatin (control, n = 19). After a follow-up period of 31 +/- 14 months, BNP (median [25th, 75th percentile]) significantly decreased in the atorvastatin group (84 [36, 186] to 55 [37, 91] pg/mL, P = .02) but not in the control group. Left ventricular end-diastolic dimension significantly decreased (67.1 [59.9, 70.8] to 61.1 [58, 63.9] mm, P = .02), and LVEF also significantly increased in the atorvastatin group (33.3% +/- 7.4% to 39.1% +/- 12.1%, P = .01) but not in the control group.Long-term atorvastatin therapy decreases neurohumoral activation and improves cardiac function in patients with mild to moderate CHF.