Pest sequences in nuclear proteins.

1. Most of proteins which are rapidly degraded inside eukaryotic cells have been found to contain amino acid sequences (PEST sequences) enriched in proline, acidic residues (glutamic acid and/or aspartic acid) and hydrophilic residues (serine and threonine) (Rogers et al. (1986) Science 234, 364-368). 2. This correlation was tested on nuclear proteins and a close relationship was found between nuclear protein stability and the presence of PEST regions. 3. Nuclear proteins with structural functions which can be considered as stable components of cell nuclei generally lack PEST sequences. 4. In contrast, regulatory nuclear factors which have specific and transient functions generally possess at least one PEST sequence.