An Investigation of the Role of the NuA4 and Swr1 Complexes in Coordination of Transcription and RNA Splicing

Abstract

RNA splicing is a critical step in gene expression in which non‐protein coding introns are removed from newly transcribed RNA. RNA splicing is carried out by the dynamic spliceosome and may occur directly after or concurrent with transcription, suggesting a close relationship between these processes. Indeed, there is mounting evidence that transcription and RNA splicing are coordinated, however the mechanistic details underlying this coordination are still lacking. The NuA4 protein complex is a histone acetylation transferase (HAT) with known functions in transcription. NuA4 works in conjunction with Swr1, an ATP‐dependent chromatin remodeling enzyme. Histone acetylation by NuA4 recruits Swr1, which subsequently exchanges H2A for the variant histone H2AZ to activate transcription. Together, these complexes regulate the transcription of ribosomal protein genes (RPGs), which comprise a substantial proportion of the genes that contain introns in Saccharomyces cerevisiae. Thus, NuA4 and Swr1 are perfectly positioned to link transcription and RNA splicing. We identified genetic interactions between genes encoding spliceosome proteins and genes encoding components of the NuA4 (eaf3Δ, eaf7Δ) and Swr1 complexes (vps72Δ and swr1Δ), as well as HTZ1, which encodes H2AZ. Splicing‐specific microarray analysis and reverse transcription‐PCR studies revealed splicing defects in swr1Δ, eaf7Δ, and htz1Δ. In addition, as predicted by our genetic studies, the splicing defects in strains harboring deletions in splicing proteins were exacerbated by deletion of EAF7, SWR1 or HTZ1. These data support a role for NuA4 and Swr1 in RNA splicing. We are currently using chromatin immunoprecipitation assays to test whether NuA4 and Swr1 increase splicing efficiency by recruiting splicing proteins during transcription. Our preliminary results indicate that splicing factor recruitment is altered in the absence of EAF7. Together, these data support a model in which the NuA4 and Swr1 chromatin modification complexes interact with the splicing machinery to coordinate transcription and splicing.Support or Funding InformationCottrell College Science Award from the Research Corporation for Science Advancement (#20186)