ALS-linked FUS mutants affect the localization of U7 snRNP and replication-dependent histone gene expression in human cells

Ankur Gadgil,Agata Stępień,Christopher E Shaw,Marc-David Ruepp,Jonas Mechtersheimer,Katarzyna Dorota Raczyńska,Agnieszka Walczak,Agnes Lumi Nishimura

doi:10.1038/s41598-021-91453-3

Abstract

Genes encoding replication-dependent histones lack introns, and the mRNAs produced are a unique class of RNA polymerase II transcripts in eukaryotic cells that do not end in a polyadenylated tail. Mature mRNAs are thus formed by a single endonucleolytic cleavage that releases the pre-mRNA from the DNA and is the only processing event necessary. U7 snRNP is one of the key factors that determines the cleavage site within the 3ʹUTR of replication-dependent histone pre-mRNAs. We have previously showed that the FUS protein interacts with U7 snRNA/snRNP and regulates the expression of histone genes by stimulating transcription and 3ʹ end maturation. Mutations in the FUS gene first identified in patients with amyotrophic lateral sclerosis (ALS) lead to the accumulation of the FUS protein in cytoplasmic inclusions. Here, we report that mutations in FUS lead to disruption of the transcriptional activity of FUS and mislocalization of U7 snRNA/snRNP in cytoplasmic aggregates in cellular models and primary neurons. As a consequence, decreased transcriptional efficiency and aberrant 3ʹ end processing of histone pre-mRNAs were observed. This study highlights for the first time the deregulation of replication-dependent histone gene expression and its involvement in ALS.

Highlights

During the evolution of eukaryotes, molecular mechanisms were established to ensure accurate assembly of newly replicated DNA into chromatin
In line with the previous results obtained from SH-SY5Y cells, we again observed that U7 snRNA was recruited into cytoplasmic aggregates along with the mutant fused in sarcoma (FUS) (Supplementary Fig. S1A)
We further investigated how amyotrophic lateral sclerosis (ALS)-linked mutations in the FUS gene can lead to disruption of the transcriptional activity of FUS and mislocalization of U7 snRNA/snRNP in cytoplasmic aggregates

Summary

Introduction

During the evolution of eukaryotes, molecular mechanisms were established to ensure accurate assembly of newly replicated DNA into chromatin. Replication-dependent histone mRNAs are not polyadenylated, and 3ʹ end processing relies only on a single cleavage event that is carried out by the endonuclease CPSF73 and mediated by a subset of specialized factors that recognize specific elements on the nascent t ranscripts[4,5,6]. Several of these factors are cell cycle-regulated, and their highest activity is in the S phase of the cell cycle[7,8,9]. FUS cytoplasmic aggregates sequester U snRNPs (U1 snRNPs, U2 snRNPs, U1 snRNA, U11 snRNA and U12 snRNA), FUS-binding proteins (hnRNP A1, hnRNP A2, and SMN), and poly(A) mRNAs37–44

Methods

Results

Conclusion