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Abstract
The zinc finger protein RE-1 silencing transcription factor (REST) is a transcriptional
repressor that represses neuronal genes in non-neuronal tissues. A neuronal splice
form of REST, termed REST4, has been described in the rat. It encompasses the N-terminus
of REST, including the N-terminal repressor domain and five of the eight zinc fingers
of the DNA-binding domain. The biological function of REST4 is controversial. Transcriptional
repression as well as transcriptional de-repression activity has been attributed to
the REST4 protein of rat. Here, we have expressed a 'humanized' version of REST4 (hREST4)
to facilitate a comparison of the biological functions of hREST4 and REST. The biological
activity the human REST protein has been extensively studied in the past. Additionally,
hREST4 has a high degree of homology with the REST4 protein of rat. An immunofluorescence
analysis showed that hREST4 is expressed in the nucleus, indicating that the protein
may have a potential impact on gene regulation. We analyzed the biological function
of hREST4 in NS20Y neuroblastoma cells using human synapsin I promoter/reporter gene
constructs. The human synapsin I gene is negatively regulated by REST. The results
show that hREST4, in contrast to the full-length human REST protein, does not impair
human synapsin I promoter activity. Moreover, co-transfection experiments with expression
vectors encoding REST and hREST4 did not reveal any evidence that REST4 blocks the
transcriptional repression activity of REST.