], were recently described (6, 7). Thus, it is evident that protein inheritance is a widespread phenomenon, at least in lower eukaryotes.The discovery of prions in yeast occurred in different ways. Some (i.e., [PSI + ] and [URE3]) were long known as genetic determinants of mysterious nature until their prion nature was proposed (8). The others were revealed by purposeful screening of potentially prionogenic proteins and corresponding determinants. The prion-like determinant [ISP + ], described in our earlier work (9), belongs to the first group, because it was detected as a nonchromosomal antisuppressor in strains containing specific sup35 nonsense suppressor mutations and the nonsense mutations his7-1 (UAA) and lys2-87 (UGA (Fig. 1A). The Sup + phenotype cosegregated with Ura + in tetrads of the diploid that was obtained by crossing the sfp1Δ and [ISP + ] strains (Fig. 1B). These findings indicate either that [ISP + ] is a prion form of Sfp1 or that the change in phenotype was caused by an independent manifestation of the SFP1-null allele.To distinguish between these two possibilities, the sfp1Δ strain was transformed with the centromeric vector pRS315-SFP1. Introduction of the wild-type SFP1 allele did not change the phenotype of the sfp1Δ strain [i.e., the absolute majority (556 of 559) of transformants has retained the Sup + phenotype]. This fact suggests that the change of phenotype in the sfp1Δ strain was caused by [ISP + ] loss rather than phenotypic effects of the SFP1 deletion; otherwise, restoration of the Sup − phenotype would be observed. Notably, this loss was irreversible, because we have not observed a single example of Sup -clones appearing in the mitotic progeny of sfp1Δ strains in contrast to [isp -] strains obtained by GuHCl treatment, which produced Sup -clones at a high frequency (9). These results confirmed that SFP1 could be considered as a likely host gene for [ISP + ].

The article studies a way of enhancing student cognition by using interdisciplinary project-based learning (IPBL) in a higher education institution. IPBL is a creative pedagogic approach allowing students of one area of specialisation to develop projects for students with different academic profiles. The application of this approach in the Ural State University of Economics resulted in a computer-assisted learning system (CALS) designed by IT students. The CALS was used in an analytical chemistry course with students majoring in Commodities Management and Expertise ('expert' students). To test how effective the technology was, the control and experimental groups were formed. In the control group, learning was done with traditional methods. In the experimental group, it was reinforced by IPBL. A statistical analysis of the results, with an application of Pearson x 2 test, showed that the cognitive levels in both IT and 'expert' experimental groups improved as compared with the control groups. The findings demonstrated that IPBL can significantly enhance learning. It can be implemented in any institution of higher or secondary education that promotes learning, including the CALS development and its use for solving problems in different subject areas.

The eukaryotic translation termination factor eRF3 stimulates release of nascent polypeptides from the ribosome in a GTP-dependent manner. In most eukaryotes studied, eRF3 consists of an essential, conserved C-terminal domain and a nonessential, nonconserved N-terminal extension. However, in some species, this extension is required for efficient termination. Our data show that the N-terminal extension of Saccharomyces cerevisiae eRF3 also participates in regulation of termination efficiency, but acts as a negative factor, increasing nonsense suppression efficiency in sup35 mutants containing amino acid substitutions in the C-terminal domain of the protein.

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Two cytoplasmically inherited determinants related by their manifestation to the control of translation accuracy were previously described in yeast. Cells carrying one of them, [PSI+], display a nonsense suppressor phenotype and contain a prion form of the Sup35 protein. Another element, [PIN+], determines the probability of de novo generation of [PSI+] and results from a prion form of several proteins, which can be functionally unrelated to Sup35p. Here we describe a novel nonchromosomal determinant related to the SUP35 gene. This determinant, designated [ISP+], was identified as an antisuppressor of certain sup35 mutations. We observed its loss upon growth on guanidine hydrochloride and subsequent spontaneous reappearance with high frequency. The reversible curability of [ISP+] resembles the behavior of yeast prions. However, in contrast to known prions, [ISP+] does not depend on the chaperone protein Hsp104. Though manifestation of both [ISP+] and [PSI+] is related to the SUP35 gene, the maintenance of [ISP+] does not depend on the prionogenic N-terminal domain of Sup35p and Sup35p is not aggregated in [ISP+] cells, thus ruling out the possibility that [ISP+] is a specific form of [PSI+]. We hypothesize that [ISP+] is a novel prion involved in the control of translation accuracy in yeast.