Translational control of gene expression in maturing erythroid cells

mRNA翻译的调控对红系细胞至关重要，因为它们的前体在核排斥的情况下失去了mRNA的合成能力。我们研究的网织细胞15-脂氧合酶（r15-LOX） mRNA的时间翻译沉默就是其中的代表。最近，我们以人K562细胞为基础，建立了一个可诱导的红细胞系统，该系统表现出红细胞终末成熟的形态学和蛋白表达变化：核排斥，hr15-LOX的表达受hnRNP K和hnRNP E1调控，线粒体丢失。利用该系统，我们发现了参与80S核糖体形成的新相互作用因子，以及迄今为止未知的与hnRNP K和hnRNP E1合作维持hr15-LOX mRNA沉默的蛋白，现在将对其进行表征。此外，除了hr15-LOX-和c-Src mRNA外，我们还发现了新的mRNA，这些mRNA在成熟过程中在含有hnRNP k的mRNA中差异富集。这种相互作用与蛋白质表达的功能相关性将被研究。我们可以证明hnRNP K和hnRNP E1在K562细胞诱导过程中被降解，并检测到hnRNP K的特异性肽。我们将鉴定和表征hnRNP K的切割活性，并研究hnRNP E1在红细胞成熟过程中是如何加工的。

Regulation of mRNA translation is essential for erythroid cells because their precursors loose mRNA synthesis capacity with nuclear exclusion. Temporal translational silencing of reticulocyte 15-Lipoxygenase (r15-LOX) mRNA, which we have studied is representative for that. Recently, based on human K562 cells we set up an inducible erythroid cell system, which exhibits changes in morphology and protein expression that are characteristic for terminal erythroid cell maturation: nuclear exclusion, expression of hr15-LOX regulated by hnRNP K and hnRNP E1 and loss of mitochondria. Employing this system we identified new interacting factors involved in 80S ribosome formation and so far unknown proteins cooperating with hnRNP K and hnRNP E1 in maintaining hr15-LOX mRNA silencing, which will now be characterized. Furthermore, besides hr15-LOX- and c-Src mRNA we identified new mRNAs, which are differentially enriched in hnRNP K-containing mRNPs during maturation. The functional relevance of this interaction for protein expression will be studied. We could show that hnRNP K and hnRNP E1 are degraded during K562 cell induction and detected a specific peptide for hnRNP K. We will identify and characterize the hnRNP K cleaving activity and investigate how hnRNP E1 is processed in erythroid cell maturation.