IISc researchers decode how a virus hijacks host protein machinery
Researchers at the Indian Institute of Science (IISc) in Bengaluru have decoded how the encephalomyocarditis virus (EMCV) hijacks a host’s protein synthesis machinery. EMCV is
Researchers at the Indian Institute of Science (IISc) in Bengaluru have decoded how the encephalomyocarditis virus (EMCV) hijacks a host’s protein synthesis machinery. EMCV is a rodent-borne animal virus that causes heart and brain inflammation, reproductive problems, and neurological disorders in many mammals. According to the researchers, viruses lack their own molecular machinery required for protein synthesis. Instead, they hijack the host’s protein-making machinery, specifically ribosomes and translational factors. Viral multiplication “This process is essential for viral multiplication and infection. Viruses have RNA genomes or mRNAs containing structured regions called Internal Ribosomal Entry Sites (IRES), which help capture the host ribosome to translate viral genes while the translation of host genes is blocked,” it said.
In a new study published in eLife, the researchers used cryo-electron microscopy (cryo-EM) to decode how the EMCV IRES hijacks the host’s protein synthesis machinery. IISc said that targeting the IRES could open up new therapeutic strategies against this virus and similar viruses – like the poliovirus – that employ the same mechanism. IRES were initially discovered more than a decade ago in EMCV and the poliovirus. But so far, their structure and specific mechanisms by which they act remained elusive. “Nothing was known in terms of the details of how the virus captures the host ribosome — other than the translational factors involved — and exactly how it does so biochemically,” said Tanweer Hussain, associate professor in the Department of Developmental Biology and Genetics (DBG), IISc, and the corresponding author.
Pulldown strategy To address this gap, Deepakash Das, PhD student in Prof. Hussain’s lab and the first author, devised a pulldown strategy using an EMCV IRES-containing mRNA to isolate the EMCV IRES pre-initiation complex from the cell lysate of rabbit reticulocytes (immature red blood cells). This pre-initiation complex is the assembly that the viral RNA forms with the host ribosome to hijack it, marking the first step in making viral proteins. Using a specially designed bait protein, the team fished out and captured the entire IRES complex intact, including various key components of translation initiation — the 40S ribosomal subunit, the initiator tRNA, and the eIF2 (eukaryotic initiation factor 2) comple from the cell lysate, and then examined it using cryo-EM “Early purification attempts went well — something of a beginner’s luck — but many subsequent rounds failed to produce usable results.
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