bicoid mRNA localization signal: phylogenetic conservation of function and RNA secondary structure.
bicoid mRNA localization signal: phylogenetic conservation of function and RNA secondary structure.
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作者：
P. Macdonald
bicoid （bcd）基因的转录本定位于果蝇卵母细胞的前极，从而允许在胚胎中形成bcd蛋白形态原的前后梯度。我们之前的研究表明，bcd mRNA 3'非编码区的630个核苷酸部分对于这种定位是必要的，并且足以赋予异源转录物的前定位。在这里，我使用了比较分析来开始更精确地定义顺式作用的mRNA定位信号。克隆了另外6种果蝇的bcd基因，并对其3′非编码区DNA进行了测序。其中3个区域在D. melanogaster中进行了特异性间mRNA定位测试，每个区域功能正常；因此，这些区域必须包含顺式作用信号。原始序列与D. melanogaster基因的差异高达50%，在大部分地区显示出斑块同源性。有趣的是，这七个物种都可能形成一个大型的刻板的二级结构。这种结构可能是定位信号的候选者，可以用于合理设计突变来测试这种可能性。
Transcripts of the bicoid (bcd) gene are localized to the anterior pole of the Drosophila oocyte, thereby allowing formation in the embryo of an anteroposterior gradient of the bcd protein morphogen. We previously showed that a 630 nucleotide portion of the 3' noncoding region of the bcd mRNA is necessary for this localization, and is sufficient to confer anterior localization on a heterologous transcript. Here I have used a comparative analysis to begin to more precisely define the cis-acting mRNA localization signal. The bcd genes from six additional Drosophila species were cloned, and DNA of the 3' noncoding regions sequenced. Three of these regions were tested interspecifically for mRNA localization in D. melanogaster and each functioned correctly; these regions must therefore contain the cis-acting signal. The primary sequences, which are up to 50% divergent from the D. melanogaster gene, show patchy homology throughout most of the region. Interestingly, all seven species can potentially form a large stereotypic secondary structure. This structure is a likely candidate for the localization signal and can be used for the rational design of mutations to test that possibility.