Ribosomal Proteins RPLP1 and RPLP2 are Host Factors Critically Required for Flavivirus Infectivity by Promoting Efficient Viral Translation Elongation.

The Flavivirus genus contains several arthropod-borne viruses that pose global health threats, including dengue virus (DENV). We identified two ribosomal proteins, RPLP1 and RPLP2 (RPLP1/2), that are crucial host factors required for translation of flaviviruses and efficient flavivirus infection of human cell lines and Aedes aegypti mosquitoes, which are natural vectors for these viruses. We hypothesized that RPLP1/2 are accessory ribosomal proteins that function to promote translation of specific cellular mRNAs sharing undefined features with the DENV genome. We found that these proteins are not broadly required for cellular translation and but are necessary for efficient accumulation of DENV proteins early in infection and ectopically expressed DENV structural proteins. The ribosome profiling technique allowed us to quantitative map ribosomes across the transcriptome during early DENV infection in human cell lines depleted for RPLP1/2. We observed that local ribosome occupancy is altered in the viral open reading frame with RPLP1/2 knockdown, consistent with a role for RPLP1/2 in promoting translation elongation. The most prominent ribosome pausing site in the DENV RNA was in the 5’ end of the E protein coding sequence which is located 210 nts downstream of two adjacent TMs. We also observed that RPLP1/2 depletion resulted in altered ribosome density in mRNAs encoding two or more transmembrane domains. This work increases our knowledge on DENV translation regulation and sheds light on the function of RPLP1/2 in translation of specific cellular RNAs.