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A gene with an open reading frame encoding a protein of 417 amino acid residues with a Gly-Thr repeat was isolated from the yeast Saccharomyces cerevisiae by using synthetic oligonucleotides encoding three Gly-Thr dimers as probes. The deduced amino acid sequence showed partial homology to the clock-affecting gene, per, of Drosophila melanogaster in the regions including the GT repeat. The function of the gene, named GTS1, was examined by characterizing the phenotypes of transformants with different copy numbers of the GTS1 gene produced either by inactivating the GTS1 gene by gene disruption (TMAgtsl) or by transformation with multicopy plasmid pPER119 (TMpGTS1). They grew at similar rates during the exponential growth phase, but the lag phases were shorter for TMAgtsl and longer for TMpGTS1 cells than that for the wild type. Analyses of their cell cycle parameters using synchronized cells revealed that the unbudding period changed as a function of gene dosage; that is, the periods of TMAgtsl and TMpGTS1 were about 20%o shorter and longer, respectively, than that of the wild-type. Another significant change in the transformants was detected in the distribution of the cell size. The mean cell volume of the TMAgtsl cells in the unbudded period (single cells) was 27% smaller than that of single wild-type cells, whereas that of single TMpGTS1 cells was 48% larger. Furthermore, in the temperature-sensitive cdc4 mutant, the GTS1 gene affected the timing of budding at the restrictive temperature. Thus, the GTS1 gene product appears to modulate the timing of budding to obtain an appropriate cell size independent of the DNA replication cycle.Among the genes known to affect biological clocks, the period gene (per) of Drosophila melanogaster (24, 37) and the frequency gene (frq) of Neurospora crassa (31) were the first to be isolated and sequenced. Characteristically, the amino acid sequences deduced from the nucleotide sequences of both genes each contained a Gly-Thr/Ser repeat which is shared by proteoglycans comprising a polysaccharide attachment site (31,37,43). Although the GT repeats are polymorphic in length and in sequence among the species of Drosophila (10,11,16,34,35,48,51), the presence of the GT repeat in the clockaffecting genes from evolutionarily remote species, Drosophila and Neurospora species, implies that this sequence plays an important role in most, if not all, clock-affecting proteins.The nature of per mutant phenotypes suggested that the gene product is an integral component of the circadian clock: mutations either shorten (pers), lengthen (per'), or abolish (per0) not only the period of circadian rhythms (19) but also the rhythm with a much shorter period during the male courtship song (26,52). Furthermore, the period of the circadian rhythm of D. melanogaster changes depending upon the gene dose (4,12,45

In the yeast Saccharomyces cerevisiae, ultradian oscillations of energy metabolism have been observed in continuous cultures. Here, we found that the level of the GTS1 gene product oscillated in concert with the ultradian rhythm of energy metabolism. When GTS1 was inactivated by gene disruption, the metabolic oscillation was affected severely, mostly disappearing within a day, in the absence of synchronized stressresponse oscillations throughout the continuous culture. The disappearance of biological rhythms in the GTS1-deleted mutant was substantially rescued by transformation with chimera plasmids carrying GTS1 under the control of GTS1's own promoter. On the other hand, this disappearance was not rescued by constitutive expression of GTS1 under the control of the triose phosphate isomerase promoter. ß

The conduction-electron state in a ferromagnetic semiconductor is studied theoretically by applying the coherent-potential approximation to the s-f model. In order to consider multiple scattering at ferromagnetic temperatures, we first derive the t-matrix elements of the s-f exchange interaction for a single f spin embedded in the effective medium, where a conduction electron is subjected to complex potential, ⌺ ↑ or ⌺ ↓ , according to the orientation of its spin. Using the mean-field theory for fluctuating f spins, the variation of the density of states with temperature is investigated for various values of IS/W. Here IS is the exchange interaction energy and W is the bandwidth of the conduction band. The anomalous redshift of the optical-absorption edge and the temperature dependence of the electron-spin polarization, experimentally observed in EuO and EuS, can be explained consistently within this approximation.

Valproic acid (VPA) inhibited the growth of yeast in a dose-dependent manner with complete inhibition attained at 100 mM. When cells were exposed to 25 mM VPA, the wild-type died showing apoptotic markers, while yca1D deleted of YCA1 encoding yeast caspase 1 survived. On the other hand, when cells were exposed to 50 mM VPA, both the wild-type and yca1D died showing morphological features similar to those of the autophagic death of cdc28 which was also independent of YCA1. Thus, these results suggested that yeast cells die via YCA1-dependent apoptosis when their proliferative activity is mildly impaired.