Geng Cuiyun, Macdonald Paul M
Institute for Cellular and Molecular Biology, Section of Molecular Cell and Developmental Biology, The University of Texas at Austin, Austin, TX 78712-0159, USA.
Mol Cell Biol. 2006 Dec;26(24):9508-16. doi: 10.1128/MCB.01136-06. Epub 2006 Oct 9.
Localization and translational control of Drosophila melanogaster gurken and oskar mRNAs rely on the hnRNP proteins Squid and Hrp48, which are complexed with one another in the ovary. Imp, the Drosophila homolog of proteins acting in localization of mRNAs in other species, is also associated with Squid and Hrp48. Notably, Imp is concentrated at sites of gurken and oskar mRNA localization in the oocyte, and alteration of gurken localization also alters Imp distribution. Imp binds gurken mRNA with high affinity in vitro; thus, the colocalization with gurken mRNA in vivo is likely to be the result of direct binding. Imp mutants support apparently normal regulation of gurken and oskar mRNAs. However, loss of Imp activity partially suppresses a gurken misexpression phenotype, indicating that Imp does act in control of gurken expression but has a largely redundant role that is only revealed when normal gurken expression is perturbed. Overexpression of Imp disrupts localization of gurken mRNA as well as localization and translational regulation of oskar mRNA. The opposing effects of reduced and elevated Imp activity on gurken mRNA expression indicate a role in gurken mRNA regulation.
黑腹果蝇中gurken和oskar mRNA的定位及翻译控制依赖于hnRNP蛋白Squid和Hrp48，它们在卵巢中相互结合。Imp是其他物种中参与mRNA定位的蛋白质的果蝇同源物，也与Squid和Hrp48相关联。值得注意的是，Imp集中在卵母细胞中gurken和oskar mRNA的定位位点，gurken定位的改变也会改变Imp的分布。Imp在体外以高亲和力结合gurken mRNA；因此，在体内与gurken mRNA的共定位可能是直接结合的结果。Imp突变体表面上支持gurken和oskar mRNA的正常调控。然而，Imp活性的丧失部分抑制了gurken错误表达表型，表明Imp确实在控制gurken表达中起作用，但具有很大程度上的冗余作用，只有在正常的gurken表达受到干扰时才会显现出来。Imp的过表达会破坏gurken mRNA的定位以及oskar mRNA的定位和翻译调控。Imp活性降低和升高对gurken mRNA表达的相反作用表明其在gurken mRNA调控中发挥作用。
