Volume 16, Number 16,
Issue of August 15, 1996
pp. 5026-5036
Copyright ©1996 Society for Neuroscience
Two Alternative Promoters Direct Neuron-Specific Expression of
the Rat Microtubule-Associated Protein 1B Gene
Received April 10, 1996; revised May 31, 1996; accepted June 3, 1996.
Dong Liu and
Itzhak Fischer
Department of Neurobiology and Anatomy, Medical College of
Pennsylvania and Hahnemann University, Philadelphia, Pennsylvania
19129
Microtubule-associated protein 1B (MAP1B) is a major constituent of
the neuronal cytoskeleton that is expressed at high levels during early
brain development and plays a role in axonal growth and neuronal
plasticity. Previous studies suggested that the regulation of its gene
expression is primarily at the transcriptional level. Thus, the
characterization of the promoter region should help to define
regulatory elements that control neuron-specific and developmental
expression of the MAP1B gene. We have isolated genomic clones
containing up to 11 kb of the upstream region of the rat MAP1B gene,
sequenced ~1.8 kb upstream from the translation start codon, and
identified several consensus sequences. These sequences include a
consensus element common to several neuronal genes, a TCC repeat, a
cAMP response element, and two TATA boxes that were 134 nucleotides
apart from each other. S1 nuclease and RNase protection assays
identified two corresponding groups of transcription initiation sites
that were used selectively in distinct regions of the nervous system
and during different stages of development. Transient transfection
assays with neuronal and non-neuronal cell lines demonstrated that each
TATA sequence and its corresponding adjacent region could independently
direct neuron-specific expression of a reporter gene. Furthermore, the
transcription of the reporter gene was initiated from the same sites as
those of the MAP1B gene in vivo. These results suggest that
two alternative and overlapping promoters, one inducible and the other
constitutive, regulate the temporal and tissue-specific expression of
the rat MAP1B gene.
Key words:
gene expression;
alternative promoters;
MAP1B;
transcription;
TATA box;
transient transfection;
cAMP-response
element