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Interaction between yeast Sup45p ( eRF1) and Sup35p (eRF3) polypeptide chain release factors: implications for prion-dependent regulation. Paper-984099. Similarly to Sup35p, in [PSI+] cells Sup45p was found in aggregates. Paper-984099.
The incorporation of Sup45p into the aggregates should inhibit its activity. Paper-984099.
This phenomenon represents a novel mechanism of regulation of gene expression at the posttranslational level.
In this study, we observed that the N domain, alone or as a part of larger fragments, can form aggregates in [PSI+] cells.
In a [PSI+] state, Sup35p forms high-molecular-weight aggregates which may inhibit Sup35p activity, leading to the [PSI+] phenotype. Paper-984099.
Two sites for Sup45p binding were found within Sup35p: one is formed by the N and M domains, and the other is located within the C domain. Paper-984099.
The SUP45 and SUP35 genes of Saccharomyces cerevisiae encode polypeptide chain release factors eRF1 and eRF3, respectively. Paper-984099.
The N domain of Sup35p, responsible for its aggregation in [PSI+] cells, may thus act as a repressor of another polypeptide chain release factor, Sup45p. Paper-984099.
The aggregation of Sup45p is caused by its binding to Sup35p and was not observed when the aggregated Sup35p fragments did not contain sites for Sup45p binding. Paper-984099.
Sup35p is composed of the N-terminal domain (N) required for [PSI+] maintenance, the presumably nonfunctional middle region (M), and the C-terminal domain (C) essential for translation termination. Paper-984099.
It has been suggested that the Sup35 protein ( Sup35p) is subject to a heritable conformational switch, similar to mammalian prions, thus giving rise to the non-Mendelian [PSI+] nonsense suppressor determinant. Paper-984099.
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iHOP - Information Hyperlinked over Proteins .
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