Control of mRNA-binding protein (mRBP) and mRNP function by Y RNAs

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The regulation of mRNA fate is essentially controlled by the interplay of mRNA-binding proteins (mRBPs) and trans-acting noncoding RNAs including microRNAs and lncRNAs (long noncoding RNAs). In the cytoplasm, the regulation of mRNA translation and turnover is largely regulated via mRNPs comprising mRNA-specific mRBP-assemblies. In recent studies, we identified that various mRBPs associate with noncoding Y RNAs. The Y3** promotes the 3-end processing of replication dependent histone pre-mRNA by modulating the assembly of CPSF-associated complexes and their delivery to histone locus bodies (HLBs), the site of histone mRNA synthesis and 3-end processing. In contrast to Y3**, Y1 as well as Y3 are mainly cytoplasmic. Both Y RNAs associate with various mRBPs in Y RNPs comprising mRBPs largely associating via the single-stranded loop of Y RNAs, Ro60 binding at the stem and La associating via a polyU-rich stretch at Y RNAs 3-end. We propose that Y RNPs are essential modulators of mRNP assembly controlling the subcellular sorting of mRBPs, their turnover, post-translational modification and/or complex formation. Accordingly, Y RNPs are expected to modulate the cytoplasmic fate of mRNAs and thus the post-transcriptional control of gene expression by scaffolding, sequestering and/or chaperoning mRBPs. This proposal aims at deciphering the molecular mechanisms underlying Y RNP-directed regulation of mRNP/mRBP function by focusing on the following aspects: 1) Characterization and validation of the Y RNA protein-interactome; 2) The role of Y RNAs in modulating the mRNP-association of mRBPs; 3) The role of Y RNAs in modulating subcellular sorting of mRBPs; 4) The role of Y RNAs in modulating mRBP protein turnover and modification; 5) The role of Y RNAs in controlling mRBP-directed control of cytoplasmic mRNA fate. We expect that the proposed studies will reveal important insights into the regulation of mRBP/mRNP function, in particular in cancer-derived cells. In the latter, upregulated expression of Y RNAs, in particular Y1 and Y3 along with several mRBPs has been reported. Accordingly, the proposed studies will set the stage for evaluating the role of Y RNA-controlled mRBP/mRNP function in cancer.