Gene regulation by chromatin remodelling complexes : SWI/SNF complex in mRNA processing and B-WICH complex in ribosomal gene expression

Sammanfattning: The aim of this project is to investigate the roles of chromatin remodelling complexes in gene regulation. It is focused on two groups of chromatin complexes: the mammalian BRG1 and BRM SWI/SNF complexes and the ISWI-containing B-WICH complex.Study 1 investigates the role of SWI/SNF complexes in alternative splicing. We show that the presence of the ATPase core subunits Brg1 and Brm influence the alternative splicing outcome of a subset of genes. We show that Brg1 and Brm interact with several splicing related factors in the nascent RNA, and that the recruitment of some of these factors to their target sites is regulated by the presence of Brg1 and Brm. We propose that SWI/SNF ATPases can modulate the interactions of RNA binding factors to the nascent RNA and in that way alter alternative splicing outcome.Study 2 focuses on SWI/SNF complexes and their influence on cleavage and polyadenylation of mRNA. We show that Brg1 and Brm interact with subunits of the cleavage and polyadenylation complexes in the nascent mRNA. SWI/SNF complexes facilitate the recruitment of the cleavage and polyadenylation complex to the polyadenylation site in a subset of genes, and this results in a more efficient cleavage and polyadenylation.Study 3 shows that B-WICH is required for ribosome gene transcriptional activation upon glucose stimulation. WSTF and SNF2h, two of the B-WICH subunits, are needed to establish an active chromatin state in the RNA pol I gene promoter when the glucose concentration is raised after a period of deprivation. We propose that it counteracts the silent, poised chromatin state imposed by the silencing chromatin remodelling complex NuRD to allow for the RNA pol I machinery to bind to the promoter.These studies show that the influence of chromatin remodelling complexes upon gene expression is important for remodelling nucleosomes at the promoter, for alternative splicing, cleavage and polyadenylation and transcriptional initiation. These complexes work together with other chromatin remodelling factors, interact with other complexes and regulate their activity by affecting their recruitment dynamics.