Structure and expression of the Aplysia polyubiquitin gene

The ubiquitin-proteasome pathway, which is up-regulated in response to sens itizing treatments with serotonin (5-HT), plays a critical role in inducing long-term facilitation (LTF) of sensory-to-motor synapses in Aplysia. We c haracterized the structure of the polyubiquitin gene of Aplysia and studied its expression. At least six ubiquitin coding units exist in tandem, one o f which encodes a protein with an amino acid sequence identical to human ub iquitin. Although the synthesis of polyubiquitin is induced by strong stimu li in many organisms, we found that the expression of ubiquitin in Aplysia is not affected by protocols that produce LTF. (C) 2000 Published by Elsevi er Science B.V. All rights reserved.