Wagner, E. J. | bioRxiv Science

bioRxiv2017

Integrator Subunit 4 is a ‘Symplekin-like’ Scaffold that Associates with INTS9/11 to Form the Integrator Cleavage Module

Integrator (INT) is a transcriptional regulatory complex associated with RNA polymerase II that is required for the 3-end processing of both UsnRNAs and enhancer RNAs. Integrator subunits 9 (INTS9) and INTS11 constitute the catalytic core of INT and are paralogues of the cleavage and polyadenylation specificity factors CPSF100 and CPSF73. While CPSF73/100 are known to associate with a third protein called Symplekin, there is no paralog of Symplekin within INT raising the question of how INTS9/11 associate with the other INT subunits. Here, we have identified that INTS4 is a specific and conserved interaction partner of INTS9/11 that does not interact with either subunit individually. Although INTS4 has no significant homology with Symplekin, it possesses N-terminal HEAT repeats similar to Symplekin but also contains a {beta}-sheet rich C-terminal region, both of which are important to bind INTS9/11. We assess three functions of INT including UsnRNA 3-end processing, maintenance of Cajal body integrity, and formation of histone locus bodies to conclude that INTS4/9/11 are the most critical of the INT subunits for UsnRNA biogenesis. Altogether, these results indicate that INTS4/9/11 compose a heterotrimeric complex that likely represents the Integrator cleavage module responsible for its endonucleolytic activity.

molecular biology↗

bioRxiv2017

Poly(A)-ClickSeq: click-chemistry for next-generation 3´-end sequencing without RNA enrichment or fragmentation

The recent emergence of alternative polyadenylation (APA) as an engine driving transcriptomic diversity has stimulated the development of sequencing methodologies designed to assess genome-wide polyadenylation events. The goal of these approaches is to enrich, partition, capture, and ultimately sequence poly(A) site junctions. However, these methods often require poly(A) enrichment, 3{acute} linker ligation steps, and RNA fragmentation, which can necessitate higher levels of starting RNA, increase experimental error, and potentially introduce bias. We recently reported a click-chemistry based method for generating RNAseq libraries called \"ClickSeq\". Here, we adapt this method to direct the cDNA synthesis specifically toward the 3{acute} UTR/poly(A) tail junction of cellular RNA. With this novel approach, we demonstrate sensitive and specific enrichment for poly(A) site junctions without the need for complex sample preparation, fragmentation or purification. Poly(A)-ClickSeq (PAC-seq) is therefore a simple procedure that generates high-quality RNA-seq poly(A) libraries. As a proof-of-principle, we utilized PAC-seq to explore the poly(A) landscape of both human and Drosophila cells in culture and observed outstanding overlap with existing poly(A) databases and also identified previously unannotated poly(A) sites. Moreover, we utilize PAC-seq to quantify and analyze APA events regulated by CFIm25 illustrating how this technology can be harnessed to identify alternatively polyadenylated RNA.

molecular biology↗