Transcriptional regulation of the shaker homolog Kv3
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The sequencing of entire genomes has brought into light the code of life, and along with it, many questions. Comparisons between whole genomes revealed that far less material is dedicated to sequencing proteins than previously believed and that the commonality between the genes that different species have is far greater than suspected. Humans share with mice, nearly every gene. The key differences between the two organisms lay in the transcriptional control regions that dictate the expression of those genes. Kv3 is a member of the Shaker cognate family of potassium ion channels found in Drosophila. These channels are involved in establishing the membrane voltage polarity in excitable tissues. The regulatory region for Kv3 was cloned from genomic DNA and core promoter elements identified. Two distinct promoters were mapped. The same genomic region was cloned from other species of fruit flies and sequenced. These were then used as input for bioinformatics applications to find regions of conserved sequences. Seven distinct blocks of sequence were found. It was reasoned that these are conserved through some functional constraint against variation. The function of these regions was tested in vivo and discrete regions were shown to regulate expression in the central and peripheral nervous systems. A specific element was found that directs expression in the antennomaxillary sensory structures. A fourth member of the Shaker cognate family was identified and found closely related to Kv3 coding sequences.