GSE171547
The Hox transcription factor Ultrabithorax binds RNA and regulates co-transcriptional splicing through an interplay with RNA polymerase II
Transcription Factors (TFs) play a pivotal role in cell fate decision by coordinating gene expression programs. Although most TFs act at the DNA layer, few TFs bind RNA and modulate splicing. Yet, the mechanistic cues underlying TFs activity in splicing remain elusive. Focusing on the Drosophila Hox TF Ultrabithorax (Ubx), our work shed light on a novel layer of Ubx function at the RNA level. Transcriptome and genome-wide binding profiles in embryonic mesoderm and Drosophila cells indicate that Ubx regulates mRNA expression and splicing to promote distinct outcomes in defined cellular contexts. Our results demonstrate a new RNA-binding ability of Ubx. We find that the N51 amino acid of the DNA-binding Homeodomain is non-essential for RNA interaction in vitro, but is required for RNA interaction in vivo and Ubx splicing activity. Moreover, mutation of the N51 amino acid weakens the interaction between Ubx and active RNA Polymerase II (Pol II). Our results reveal that Ubx regulates elongation-coupled splicing, which could be coordinated by a dynamic interplay with active Pol II on chromatin. Overall, our work uncovered a novel role of the Hox TFs at the mRNA regulatory layer. This could be an essential function for other classes of TFs to control cell diversity. Overall design: Total RNAs were extracted from four independent replicates from Drosophila S2R+ cells expressing GFPnls, myc-UbxWT, or myc-UbxN51A (Gal4-UAS, actin promoter) using Qiagen RNA extraction kit (RNeasy). RNA quality was assessed using BioAnalyzer 2100TM (Agilent Technologies). Material handling and mRNA-Seq directional libraries were performed with the Deep-Sequencing facility in Heidelberg (Cell Networks) with TruSeq kit and poly(A) selection according to the manufacturer's protocol (Illumina). Sequencing was performed with NextSeq500 High-Output with a read-length of 75bp and single-end strands. Replicates were validated by FastQC report and 3 replicates for each sample were further selected according to Principle Component Analysis (PCA) analysis for the study.