The Human Synapsin II Gene Promoter

Abstract

Synapsin II is a neuron-specific phosphoprotein that selectively binds to small synaptic vesicles in the pre-synaptic nerve terminal. Here we report the cloning and sequencing of the 5-flanking region of the human syn-apsin II gene. This sequence is very GC-rich and lacks a TATA or CAAT box. Two major transcriptional start sites were mapped. A hybrid gene consisting of the Esch-erichia coli chloramphenicol acetyltransferase gene under the control of 837 base pairs of the synapsin II 5-upstream region was transfected into neuronal and non-neuronal cells. While reporter gene expression was low in neuroblastoma and non-neuronal cells, high chloram-phenicol acetyltransferase activities were monitored in PC12 pheochromocytoma cells. However, there was no correlation between reporter gene expression in the transfected cells and endogenous synapsin II immuno-reactivity. Using DNA-protein binding assays we showed that the transcription factors zif268/egr-1, poly-oma enhancer activator 3 (PEA3), and AP2 specifically contact the synapsin II promoter DNA in vitro. Moreover , the zif268/egr-1 protein as well as PEA3 were shown to stimulate transcription of a reporter gene containing synapsin II promoter sequences. In the nervous system, zif268/egr-1 functions as a "third messenger" with a potential role in synaptic plasticity. PEA3 is expressed in the brain and its activity is regulated by proteins encoded from non-nuclear oncogenes. We postulate that zif268/egr-1 and PEA3 couple extracellular signals to long-term responses by regulating synapsin II gene expression.