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Molecular characterization of the RNA-protein complex directing -2/-1 programmed ribosomal frameshifting during arterivirus replicase expression

DOI: 10.1074/jbc.RA120.016105 DOI Help

Authors: Ankoor Patel (University of Manitoba) , Emmely E. Treffers (Leiden University Medical Center) , Markus Meier (University of Manitoba) , Trushar R. Patel (University of Lethbridge) , Jörg Stetefeld (University of Manitoba) , Eric J. Snijder (Leiden University Medical Centre) , Brian L. Mark (University of Manitoba)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biological Chemistry , VOL 295 , PAGES 17904-17921

State: Published (Approved)
Published: December 2020
Diamond Proposal Number(s): 22113

Open Access Open Access

Abstract: Programmed ribosomal frameshifting (PRF) is a mechanism used by arteriviruses like porcine reproductive and respiratory syndrome virus (PRRSV) to generate multiple proteins from overlapping reading frames within its RNA genome. PRRSV employs -1 PRF directed by RNA secondary and tertiary structures within its viral genome (canonical PRF), as well as a noncanonical -1 and -2 PRF that are stimulated by the interactions of PRRSV non-structural protein 1β (nsp1β) and host protein poly(C)-binding protein (PCBP) 1 or 2 with the viral genome. Together, nsp1β and one of the PCBPs act as transactivators that bind a C-rich motif near the shift site to stimulate -1 and -2 PRF, thereby enabling the ribosome to generate two frameshift products that are implicated in viral immune evasion. How nsp1β and PCBP associate with the viral RNA genome remains unclear. Here, we describe the purification of the nsp1β:PCBP2:viral RNA complex on a scale sufficient for structural analysis using small-angle X-ray scattering and stochiometric analysis by analytical ultracentrifugation. The proteins associate with the RNA C-rich motif as a 1:1:1 complex. The monomeric form of nsp1β within the complex differs from previously reported homodimer identified by X-ray crystallography. Functional analysis of the complex via mutational analysis combined with RNA binding assays and cell-based frameshifting reporter assays reveal a number of key residues within nsp1β and PCBP2 that are involved in complex formation and function. Our results suggest that nsp1β and PCBP2 both interact directly with viral RNA during formation of the complex to coordinate this unusual PRF mechanism.

Journal Keywords: PRRSV; nidovirus; PCBP; nsp1beta; ribosome; structural biology; RNA virus; viral replication; virology; ribosome function

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: B21-High Throughput SAXS