The 30th International Conference on Arabidopsis Research (ICAR 2019)

555 / 2019-03-15 21:31:09

Composition and function of the Arabidopsis U1 snRNP complex

RNA,mRNA mis-splicing,intron splicing,polymerase II,transcriptional regulation,splicing,spliceosome,U1 snRNP

Plenary track > RNA Biology

Introns are removed by the spliceosome, a large macromolecular complex composed of five ribonucleoprotein subcomplexes (U snRNPs). The U1 snRNP, which binds to 5ʹ splice sites, plays an essential role in early steps of the splicing reaction. In yeast and humans, the U1 snRNP embodies also diverse roles in transcriptional and posttranscriptional gene regulation. Functions of the plant U1 snRNP beyond splicing remain to be elucidated. Here, we report the full protein interaction map and genome-wide binding patterns of the Arabidopsis U1 snRNP. Aside from the proteins involved in splicing, we found several proteins involved in transcription, polyadenylation, RNA transport, DNA damage response and epigenetic gene regulation to be associated with the Arabidopsis U1 snRNP. Conversely, we found that the U1 snRNP associates with the chromatin of intron-containing and intronless genes. Absence of U1 resulted in the reduced accumulation of polymerase II, highlighting the importance of U1 integrity for transcription. Loss of U1 function also caused a global switch in the usage of the distal and proximal polyadenylation sites in a subset of genes in Arabidopsis. Overall, our data demonstrate that the Arabidopsis U1 snRNP complex is essential for splicing, but it also regulates gene expression through the association with factors involved in transcriptional regulation and 3’ end RNA processing