Comprehensive Analysis of Nucleocytoplasmic Dynamics of mRNA in Drosophila cells

Eukaryotic mRNAs undergo a cycle of transcription, nuclear export, and degradation. A major challenge is to obtain a global, quantitative view of these processes. Here we measured the genome-wide nucleocytoplasmic dynamics of mRNA in Drosophila cells by metabolic labeling in combination with cellular fractionation. By mathematical modeling of these data we determined rates of transcription, export and cytoplasmic decay for >5,000 genes. We characterized these kinetic rates and investigated links with mRNA features, RNA-binding proteins (RBPs) and chromatin states. We found prominent correlations between mRNA decay rate and transcript size, while nuclear export rates are linked to the size of the 3''UTR. Transcription, export and decay rates are each associated with distinct spectra of RBPs. Specific classes of genes, such as those encoding cytoplasmic ribosomal proteins, exhibit characteristic combinations of rate constants, suggesting modular control. Overall, transcription and decay rates have a major impact on transcript abundance, while nuclear export is of minor importance. Finally, correlations between rate constants suggest global coordination between the three processes. Our approach should be generally applicable to other cell systems and provides insights into the genome-wide nucleocytoplasmic kinetics of mRNA. Overall design: 24 RNA-seq experiments comprising 2 biological replicates: pre-exsiting nuclear mRNA time 0h (samples 1&13), pre-exsiting nuclear mRNA time 0.5h (samples 2&14), pre-exsiting nuclear mRNA time 1.5h (samples 3&15) , pre-exsiting nuclear mRNA time 3h (samples 4&16), pre-exsiting nuclear mRNA time 5h (samples 5&17), pre-exsiting nuclear mRNA time 7.5h (samples 6&18), pre-exsiting cytoplasmic mRNA time 0h (samples 7&19), pre-exsiting cytoplasmic mRNA time 0.5h (samples 8&20), pre-exsiting cytoplasmic mRNA time 1.5h (samples 9&21) , pre-exsiting cytoplasmic mRNA time 3h (samples 10&22), pre-exsiting cytoplasmic mRNA time 5h (samples 11&23), pre-exsiting cytoplasmic mRNA time 7.5h (samples 12&24)

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Chen T, van Steensel B