Translational control of gene expression in maturing erythroid cells

由于红系细胞的前体细胞在核排异的情况下失去了信使核糖核酸的合成能力，因此调节其信使核糖核酸的翻译是必不可少的。我们所研究的网织红细胞15-脂氧合酶(R15-LOX)的瞬时翻译沉默就是其中的代表。最近，我们在人K562细胞的基础上建立了一个可诱导的红系细胞系，其形态和蛋白表达的变化是红系细胞终末成熟的特征：核排斥，由hnRNP K和hnRNP E1调控的HR15-LOX的表达，以及线粒体的丢失。利用这个系统，我们鉴定了参与80S核糖体形成的新的相互作用因子，以及迄今未知的与hnRNP K和hnRNP E1协同维持HR15-LOX mRNA沉默的蛋白质，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mRNAs，它们在成熟过程中差异地富含含hnRNP K的mRNPs。这种相互作用对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的特异性多肽。我们将鉴定和表征hnRNP K的裂解活性，并研究hnRNP E1是如何在红细胞成熟过程中被处理的。

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.