Viral regulation of host cell biology by hijacking of the nucleolar DNA-damage response

Stephen M Rawlinson,Gregory W Moseley,Toby D M Bell,Anthony W Purcell,Lin-Fa Wang,Christina L Rootes,Hans J Netter,Amanda Woon,Glenn A Marsh,Cameron R Stewart,Ashley M Rozario,Tianyue Zhao,Kim G Lieu,Paul J Mcmillan

doi:10.1038/s41467-018-05354-7

Abstract

Recent studies indicate that nucleoli play critical roles in the DNA-damage response (DDR) via interaction of DDR machinery including NBS1 with nucleolar Treacle protein, a key mediator of ribosomal RNA (rRNA) transcription and processing. Here, using proteomics, confocal and single molecule super-resolution imaging, and infection under biosafety level-4 containment, we show that this nucleolar DDR pathway is targeted by infectious pathogens. We find that the matrix proteins of Hendra virus and Nipah virus, highly pathogenic viruses of the Henipavirus genus in the order Mononegavirales, interact with Treacle and inhibit its function, thereby silencing rRNA biogenesis, consistent with mimicking NBS1–Treacle interaction during a DDR. Furthermore, inhibition of Treacle expression/function enhances henipavirus production. These data identify a mechanism for viral modulation of host cells by appropriating the nucleolar DDR and represent, to our knowledge, the first direct intranucleolar function for proteins of any mononegavirus.

Highlights

Recent studies indicate that nucleoli play critical roles in the DNA-damage response (DDR) via interaction of DDR machinery including Nijmegen Breakage Syndrome 1 (NBS1) with nucleolar Treacle protein, a key mediator of ribosomal RNA transcription and processing
The nucleolus is classically divided into three major subcompartments, the inner fibrillar center (FC), dense fibrillar component (DFC) and granular component (GC), which appear to mediate specific stages of ribosome biogenesis through distinct proteomes
We used confocal laser scanning microscopy (CLSM) to image nucleoli in cells infected by HeV and immunostained for M protein (Fig. 1a), or in living cells transfected to express HeV M protein fused to green fluorescent protein (GFP-HeV M) (Fig. 1b and Supplementary Movie 1)

Summary

Introduction

Recent studies indicate that nucleoli play critical roles in the DNA-damage response (DDR) via interaction of DDR machinery including NBS1 with nucleolar Treacle protein, a key mediator of ribosomal RNA (rRNA) transcription and processing. Recent studies of the roles of nucleoli in stress responses have identified Treacle protein, a nucleolar regulator of rDNA transcription and pre-rRNA processing that localizes to subnucleolar compartments, as a critical mediator of rRNA silencing that is induced by the DDR2,4,7–10. Other than its roles in genetic disorders such as TCS, neurodegenerative diseases[13], and cancers[14], the nucleolus is targeted by proteins expressed by diverse viruses, potentially enabling viral modulation of intranucleolar processes controlling host cell biology[15,16] This aspect of viral biology remains poorly characterized, with respect to viruses of the order Mononegavirales, which comprises non-segmented negativestrand RNA viruses including the highly pathogenic Hendra (HeV) and Nipah (NiV) viruses (genus Henipavirus, family Paramyxoviridae), rabies virus, Ebola virus, measles virus, and mumps virus. Almost all mononegaviruses mediate transcription, replication, and assembly exclusively within the cytoplasm, but several recent reports indicate that certain proteins of mononegaviruses can localize to the nucleolus and bind to specific nucleolar proteins[17,18,19]

Methods

Results

Conclusion