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Muniz L.,Wellcome Trust Center for Cell Biology | Davidson L.,University of Sheffield | West S.,University of Sheffield
Molecular and Cellular Biology | Year: 2015

Most human protein-encoding transcripts contain multiple introns that are removed by splicing. Although splicing catalysis is frequently cotranscriptional, some introns are excised after polyadenylation. Accumulating evidence suggests that delayed splicing has regulatory potential, but the mechanisms are still not well understood. Here we identify a terminal poly(A) tail as being important for a subset of intron excision events that follow cleavage and polyadenylation. In these cases, splicing is promoted by the nuclear poly(A) binding protein, PABPN1, and poly(A) polymerase (PAP). PABPN1 promotes intron excision in the context of 3'-end polyadenylation but not when bound to internal A-tracts. Importantly, the ability of PABPN1 to promote splicing requires its RNA binding and, to a lesser extent, PAP-stimulatory functions. Interestingly, an N-terminal alanine expansion in PABPN1 that is thought to cause oculopharyngeal muscular dystrophy cannot completely rescue the effects of PABPN1 depletion, suggesting that this pathway may have relevance to disease. Finally, inefficient polyadenylation is associated with impaired recruitment of splicing factors to affected introns, which are consequently degraded by the exosome. Our studies uncover a new function for polyadenylation in controlling the expression of a subset of human genes via pre-mRNA splicing. © 2015, American Society for Microbiology. Source

West S.,Wellcome Trust Center for Cell Biology
Biochemical Society Transactions | Year: 2012

Splicing is a key process for mRNA maturation, particularly in higher eukaryotes where most protein-coding transcripts contain multiple introns. It is achieved by the concerted action of five snRNAs (small nuclear RNAs) and hundreds of accessory proteins that form the spliceosome. Although snRNAs are present in equal amounts in the spliceosome, there is an overall excess of U1 in human cells. This finding led to the opinion that U1 might be involved in processes other than splicing. Research has shown that this is indeed the case and some examples found from studies in human cell systems are described briefly in the present review. ©The Authors Journal compilation ©2012 Biochemical Society. Source

Brockington S.F.,University of Cambridge | Moyroud E.,University of Cambridge | Sayou C.,Wellcome Trust Center for Cell Biology | Monniaux M.,Max Planck Institute for Plant Breeding Research | And 20 more authors.
Science | Year: 2015

Brunkard et al. propose that the identification of novel LEAFY sequences contradicts our model of evolution through promiscuous intermediates. Based on the debate surrounding land plant phylogeny and on our analysis of these interesting novel sequences, we explain why there is no solid evidence to disprove our model. Source

Davidson L.,Wellcome Trust Center for Cell Biology | Muniz L.,Wellcome Trust Center for Cell Biology | West S.,Wellcome Trust Center for Cell Biology
Genes and Development | Year: 2014

3' end formation of pre-mRNAs is coupled to their transcription via the C-terminal domain (CTD) of RNA polymerase II (Pol II). Nearly all protein-coding transcripts are matured by cleavage and polyadenylation (CPA), which is frequently misregulated in disease. Understanding how transcription is coordinated with CPA in human cells is therefore very important. We found that the CTD is heavily phosphorylated on Ser2 (Ser2p) at poly(A) (pA) signals coincident with recruitment of the CstF77 CPA factor. Depletion of the Ser2 kinase Cdk12 impairs Ser2p, CstF77 recruitment, and CPA, strongly suggesting that the processes are linked, as they are in budding yeast. Importantly, we additionally show that the high Ser2p signals at the 3' end depend on pA signal function. Down-regulation of CPA results in the loss of a 3' Ser2p peak, whereas a new peak is formed when CPA is induced de novo. Finally, high Ser2p signals are generated by Pol II pausing, which is a well-known feature of pA site recognition. Thus, a reciprocal relationship between early steps in pA site processing and Ser2p ensures efficient 3' end formation. © 2014 Davidson et al. Source

Fernius J.,Wellcome Trust Center for Cell Biology | Nerusheva O.O.,Wellcome Trust Center for Cell Biology | Galander S.,Wellcome Trust Center for Cell Biology | Alves F.D.L.,Wellcome Trust Center for Cell Biology | And 2 more authors.
Current Biology | Year: 2013

Cohesin is a conserved ring-shaped multiprotein complex that participates in chromosome segregation, DNA repair, and transcriptional regulation [1, 2]. Cohesin loading onto chromosomes universally requires the Scc2/4 "loader" complex (also called NippedBL/Mau2), mutations in which cause the developmental disorder Cornelia de Lange syndrome in humans [1-9]. Cohesin is most concentrated in the pericentromere, the region surrounding the centromere [10-15]. Enriched pericentromeric cohesin requires the Ctf19 kinetochore subcomplex in budding yeast [16-18]. Here, we uncover the spatial and temporal determinants for Scc2/4 centromere association. We demonstrate that the critical role of the Ctf19 complex is to enable Scc2/4 association with centromeres, through which cohesin loads and spreads onto the adjacent pericentromere. We show that, unexpectedly, Scc2 association with centromeres depends on cohesin itself. The absence of the Scc1/Mcd1/Rad21 cohesin subunit precludes Scc2 association with centromeres from anaphase until late G1. Expression of SCC1 is both necessary and sufficient for the binding of cohesin to its loader, the association of Scc2 with centromeres, and cohesin loading. We propose that cohesin triggers its own loading by enabling Scc2/4 to connect with chromosomal landmarks, which at centromeres are specified by the Ctf19 complex. Overall, our findings provide a paradigm for the spatial and temporal control of cohesin loading. © 2013 Elsevier Ltd. Source

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