Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU , UK ; Present address: Seattle Biomedical Research Institute, 307 Westlake Avenue N, Suite 500, Seattle, WA 98109-5219, USA.
Biol Open. 2012 May 15;1(5):488-97. doi: 10.1242/bio.2012885. Epub 2012 Apr 11.
In the Drosophila oocyte, mRNA transport and localised translation play a fundamental role in axis determination and germline formation of the future embryo. gurken mRNA encodes a secreted TGF-α signal that specifies dorsal structures, and is localised to the dorso-anterior corner of the oocyte via a cis-acting 64 nucleotide gurken localisation signal. Using GRNA chromatography, we characterised the biochemical composition of the ribonucleoprotein complexes that form around the gurken mRNA localisation signal in the oocyte. We identified a number of the factors already known to be involved in gurken localisation and translational regulation, such as Squid and Imp, in addition to a number of factors with known links to mRNA localisation, such as Me31B and Exu. We also identified previously uncharacterised Drosophila proteins, including the fly homologue of mammalian SYNCRIP/hnRNPQ, a component of RNA transport granules in the dendrites of mammalian hippocampal neurons. We show that Drosophila Syncrip binds specifically to gurken and oskar, but not bicoid transcripts. The loss-of-function and overexpression phenotypes of syncrip in Drosophila egg chambers show that the protein is required for correct grk and osk mRNA localisation and translational regulation. We conclude that Drosophila Syncrip is a new factor required for localisation and translational regulation of oskar and gurken mRNA in the oocyte. We propose that Syncrip/SYNCRIP is part of a conserved complex associated with localised transcripts and required for their correct translational regulation in flies and mammals.
在果蝇卵母细胞中，mRNA 运输和局部翻译在轴确定和未来胚胎生殖系形成中起着根本作用。gurken mRNA 编码一种分泌的 TGF-α信号，该信号指定背侧结构，并通过顺式作用的 64 个核苷酸 gurken 定位信号定位到卵母细胞的背-前角。使用 GRNA 色谱法，我们表征了在卵母细胞中形成 gurken mRNA 定位信号周围的核糖核蛋白复合物的生化组成。我们鉴定了一些已经已知参与 gurken 定位和翻译调节的因子，如 Squid 和 Imp，除了一些已知与 mRNA 定位有关的因子，如 Me31B 和 Exu。我们还鉴定了以前未表征的果蝇蛋白，包括哺乳动物 SYNCRIP/hnRNPQ 的同源物，这是哺乳动物海马神经元树突中 RNA 运输颗粒的一个组成部分。我们表明，果蝇 Syncrip 特异性结合 gurken 和 oskar，但不结合 bicoid 转录物。在果蝇卵囊中 syncrip 的功能丧失和过表达表型表明该蛋白对于正确的 grk 和 osk mRNA 定位和翻译调节是必需的。我们得出结论，果蝇 Syncrip 是卵母细胞中 oskar 和 gurken mRNA 定位和翻译调节所必需的新因子。我们提出，Syncrip/SYNCRIP 是与局部转录本相关的保守复合物的一部分，并且在果蝇和哺乳动物中对于它们的正确翻译调节是必需的。
