The Function of HASTY in Arabidopsis

分子在核膜上的运输主要受Importinβ蛋白家族成员的调节。虽然这些蛋白质在酵母和哺乳动物中的功能已经很好地描述了，但对它们在植物中的功能知之甚少。这个项目中描述的实验是为了揭示Exportin5的拟南芥同源基因HASTY的功能。Exportin5与哺乳动物miRNAs和tRNAs的核输出有关，而HASTY的突变表型表明它在植物中可能具有类似的功能。这一假设将通过检验仓促突变对miRNAs和tRNAs亚细胞分布的影响，以及通过确定仓促蛋白在体内和体外与之物理相互作用的分子来检验。已经对抑制hst-3表型的突变进行了筛选，以确定与hst-3功能相关的基因。定位克隆将被用来识别受这样一种突变SOH影响的基因，并将对其功能进行表征。目前，在存在突变等位基因的高等生物中，HASTY是Exportin5的唯一同源基因。这些突变为研究这一重要蛋白质的功能提供了一个独特的机会，也可能为miRNAs的生物发生和功能提供新的见解。

The transport of molecules across the nuclear membrane is primarily regulated by members of the importin beta family of proteins. Although the function of these proteins is well characterized in yeast and mammals, very little is known about their function in plants. The experiments described in this project are designed to reveal the function of HASTY, the Arabidopsis orthologue of Exportin5. Exportin5 has been implicated in the nuclear export of miRNAs and tRNAs in mammals, and the mutant phenotype of hasty suggests that it may have a similar function in plants. This hypothesis will be tested by examining the effect of hasty mutations on the sub-cellular distribution of miRNAs and tRNAs, and by identifying the molecules with which the HASTY protein physically interacts in vivo and in vitro. Screens for mutations that suppress the phenotype of hst-3 have been conducted in order to identify genes that are functionally related to HST. Positional cloning will be used to identify the gene affected by one such mutation, soh, and its function will be characterized. At present, HASTY is the only orthologue of Exportin5 in higher organisms for which mutant alleles exist. These mutations provide a unique opportunity to study the function of this important protein, and may provide new insights into the biogenesis and function of miRNAs as well.