Transactivation of programmed ribosomal frameshifting by a viral protein

作者：Yànhuá Lǐ, Emmely E. Treffers, Sawsan Napthine, Ali Taş, Longchao Zhu, Zhi Sun, Susanne Bell, Brian L. Mark, Peter A. van Veelen, Martijn J. van Hemert, Andrew E. Firth, Ian Brierley, Eric J. Snijder, Yīng Fāng · 发表于：Proceedings of the National Academy of Sciences · 年份：2014 · DOI：10.1073/pnas.1321930111 · 被引用次数：165 · 研究领域：Viral Infections and Immunology Research、Animal Virus Infections Studies、RNA regulation and disease

Programmed -1 ribosomal frameshifting (-1 PRF) is a widely used translational mechanism facilitating the expression of two polypeptides from a single mRNA. Commonly, the ribosome interacts with an mRNA secondary structure that promotes -1 frameshifting on a homopolymeric slippery sequence. Recently, we described an unusual -2 frameshifting (-2 PRF) signal directing efficient expression of a transframe protein [nonstructural protein 2TF (nsp2TF)] of porcine reproductive and respiratory syndrome virus (PRRSV) from an alternative reading frame overlapping the viral replicase gene. Unusually, this arterivirus PRF signal lacks an obvious stimulatory RNA secondary structure, but as confirmed here, can also direct the occurrence of -1 PRF, yielding a third, truncated nsp2 variant named "nsp2N." Remarkably, we now show that both -2 and -1 PRF are transactivated by a protein factor, specifically a PRRSV replicase subunit (nsp1β). Embedded in nsp1β's papain-like autoproteinase domain, we identified a highly conserved, putative RNA-binding motif that is critical for PRF transactivation. The minimal RNA sequence required for PRF was mapped within a 34-nt region that includes the slippery sequence and a downstream conserved CCCANCUCC motif. Interaction of nsp1β with the PRF signal was demonstrated in pull-down assays. These studies demonstrate for the first time, to our knowledge, that a protein can function as a transactivator of ribosomal frameshifting. The newly identified frameshiftin...