Project description:The generation of distiThe generation of distinct messenger RNA isoforms through alternative RNA processing influences the expression and function of genes, often in a cell-type specific manner. Here, we assess the regulatory relationships between transcription initiation, alternative splicing, and 3ʹ end site selection. Applying multiple long-read-sequencing approaches to obtain an assembly accurately representing even the longest transcripts from end to end, we quantify mRNA isoform choice in Drosophila and human tissues, including the transcriptionally complex nervous system. We find that in Drosophila brains as well as in human cerebral organoids, 3ʹ end site choice is globally influenced by the site of transcription initiation. “Dominant promoters”, characterized by specific epigenetic signatures including p300/CBP binding, impose a transcriptional constraint to define splice and polyadenylation variants. In vivo deletion or overexpression of dominant promoters as well as CBP/p300 loss disrupted the 3ʹ end expression landscape. Our study demonstrates the crucial impact of TSS choice on the regulation of transcript diversity and tissue identity.ct messenger RNA isoforms through alternative splicing and alternative 3' end formation influences the expression and function of genes, often in a cell-type specific manner. Here, we quantitatively assess the regulatory relationships between transcription initiation and co-transcriptional processing steps, particularly 3' end formation. Applying multiple long-read-sequencing approaches to obtain an assembly accurately representing even the longest mRNA isoforms from end-to-end, we quantify mRNA isoform choice in Drosophila and human tissues, including the transcriptionally complex nervous system. We find that in Drosophila brains as well as in human cerebral organoids, 3' end site choice is globally influenced by the site of transcription start. We define a subset of TSSs, “dominant promoters” that impose a transcriptional constraint to predetermine splice and polyadenylation variants, which are characterized by specific epigenetic signatures. In vivo deletion or overexpression of dominant promoters disrupted the 3' end expression landscape. Our study demonstrates the crucial impact of transcription initiation site choice on the regulation of transcript diversity and tissue identity.

Project description:The generation of distinct messenger RNA isoforms through alternative RNA processing influences the expression and function of genes, often in a cell-type specific manner. Here, we assess the regulatory relationships between transcription initiation, alternative splicing, and 3ʹ end site selection. Applying multiple long-read-sequencing approaches to obtain an assembly accurately representing even the longest transcripts from end to end, we quantify mRNA isoform choice in Drosophila and human tissues, including the transcriptionally complex nervous system. We find that in Drosophila brains as well as in human cerebral organoids, 3ʹ end site choice is globally influenced by the site of transcription initiation. “Dominant promoters”, characterized by specific epigenetic signatures including p300/CBP binding, impose a transcriptional constraint to define splice and polyadenylation variants. In vivo deletion or overexpression of dominant promoters as well as CBP/p300 loss disrupted the 3ʹ end expression landscape. Our study demonstrates the crucial impact of TSS choice on the regulation of transcript diversity and tissue identity.ct messenger RNA isoforms through alternative splicing and alternative 3' end formation influences the expression and function of genes, often in a cell-type specific manner. Here, we quantitatively assess the regulatory relationships between transcription initiation and co-transcriptional processing steps, particularly 3' end formation. Applying multiple long-read-sequencing approaches to obtain an assembly accurately representing even the longest mRNA isoforms from end-to-end, we quantify mRNA isoform choice in Drosophila and human tissues, including the transcriptionally complex nervous system. We find that in Drosophila brains as well as in human cerebral organoids, 3' end site choice is globally influenced by the site of transcription start. We define a subset of TSSs, “dominant promoters” that impose a transcriptional constraint to predetermine splice and polyadenylation variants, which are characterized by specific epigenetic signatures. In vivo deletion or overexpression of dominant promoters disrupted the 3' end expression landscape. Our study demonstrates the crucial impact of transcription initiation site choice on the regulation of transcript diversity and tissue identity.

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Sites of transcription initiation drive mRNA isoform selection

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