Activating transcription factor ⁄ cAMP response element binding protein (ATF ⁄ CREB) family transcription factors play central roles in maintaining cellular homeostasis. They are activated in response to environmental stimuli, bind to CRE sequences in the promoters of stressresponse genes and regulate transcription. Although ATF ⁄ CREB proteins are widely conserved among most eukaryotes, their characteristics are highly diverse. Here, we investigated the functions of a fission yeast ATF ⁄ CREB protein Atf21 to find out its unique properties. We show that Atf21 is dispensable for the adaptive response to several stresses such as nitrogen starvation and for meiotic events including nuclear divisions. However, spores derived from atf21D mutants are not as mature as wild-type ones and are unable to form colonies under nutrition-rich conditions. Furthermore, we demonstrate that the Atf21 protein, which is scarce in early meiosis, gradually accumulates as meiosis proceeds; it reaches maximum levels approximately 8 h after nitrogen starvation and is present during germination. These results suggest that Atf21 is expressed and functions long after nitrogen starvation. Given that other well-characterized fission yeast ATF ⁄ CREB proteins Atf1 and Pcr1 accumulate and function promptly upon exposure to environmental stresses, we propose that Atf21 is a distinct member of the ATF ⁄ CREB family in fission yeast.

No abstract

No abstract

No abstract

First-principles phase equilibria calculations often overestimate an order-disorder transition temperature due to the neglect of local lattice distortion effects originated from the mixture of elements of different atomic sizes. The lattice vibration effects introduced through the Debye-Grü neisen theory within the quasi-harmonic approximation has proven to be quite effective in circumventing the inconveniences. With the preferential enhancement of the stability of a disordered phase by introducing the lattice vibration effects, the transition temperature was reduced considerably. In order to gain further insight into the lattice vibration effects, a systematic investigation of the vibrational free energy of the Debye-Grü neisen theory is attempted on the two-dimensional square lattice which constitutes a prototype study prior to the firstprinciples calculations on realistic alloy systems. A particular focus of the present study is placed on the effects of Debye temperatures of constituent phases on the transition temperature. It is shown that lattice softening by lattice vibration stabilizes the disordered phase by reducing the energy expended to accommodate atoms of different sizes, which is manifested by the reduction of the curvature of the atomic potentials. It is, however, predicted that an opposite case can also take place. When the Debye temperature of an ordered phase is lower than that of the pure metals, the ordered phase is more stabilized and the inclusion of the lattice vibration effects in the free energy raises the resultant transition temperature.