Project description:Programmed ribosomal frameshifting is a process that augments the coding capacity of particular mRNA transcripts. Programmed ribosomal frameshifting may occur during the decoding of chromosomally encoded genes in both prokaryotes and eukaryotes. Although programmed ribosomal frameshifting has been intensively studied, less is known about the occurrence of translation errors that result in frameshifts. Detection of unexpectedly efficient frameshift suppression in E. coli (at levels ranging from 1% to 10% with two unrelated test proteins) led us to investigate the scope of events responsible for restoration of the native frame. To enable a comprehensive approach, we developed a targeted mass-spectrometry method–“translational tiling proteomics”–allowing interrogation of the full set of possible –1 slippage events that could lead to the observed instances of frameshift suppression in vitro and in cells. Our findings point to an unexpectedly high basal level of ribosomal frameshifting, suggest that frameshifted products may contribute more significantly to the proteome than generally assumed, and raise the possibility that particular pseudogenes may specify functional proteins.
Project description:Programmed ribosomal frameshifting (PRF) is a fundamental gene expression event in many viruses, including SARS-CoV-2. It allows production of essential viral structural and replicative enzymes that are encoded in an alternative reading frame. Despite the importance of PRF for the viral life cycle, it is still largely unknown how and to what extent cellular factors alter mechanical properties of frameshift elements and thereby impact virulence. This prompted us to comprehensively dissect the interplay between the SARS-CoV-2 frameshift element and the host proteome. We reveal that the short isoform of the zinc-finger antiviral protein (ZAP-S) is a direct regulator of PRF in SARS-CoV-2 infected cells. ZAP-S overexpression strongly impairs frameshifting and inhibits viral replication. Using in vitro ensemble and single-molecule techniques, we further demonstrate that ZAP-S directly interacts with the SARS-CoV-2 RNA and interferes with the folding of the frameshift RNA element. Together, these data identify ZAP-S as a host-encoded inhibitor of SARS-CoV-2 frameshifting and expand our understanding of RNA-based gene regulation.
Project description:Genome-wide CRISPR-Cas9 knockout screens were performed in dual-fluorescent frameshifting reporter cell lines to identify human host factors for SARS-CoV-2 programmed ribosomal frameshfiting.
Project description:Many positive-strand RNA viruses, including all known coronaviruses, employ programmed –1 ribosomal frameshifting (–1 PRF) to regulate the translation of polycistronic viral RNAs. However, only a few host factors have been shown to regulate –1 PRF. Through a reporter-based genome-wide CRISPR/Cas9 knockout screen, we identified several host factors that either suppressed or enhanced –1 PRF of SARS-CoV-2. One of these factors is eukaryotic translation initiation factor 2A (eIF2A), which specifically and directly enhanced –1 PRF in vitro and in cells. Consistent with the crucial role of efficient –1 PRF in transcriptase/replicase expression, loss of eIF2A reduced SARS-CoV-2 replication in cells. Transcriptome-wide analysis of eIF2A-interacting RNAs showed that eIF2A primarily interacted with 18S ribosomal RNA near the contacts between the SARS-CoV-2 frameshift-stimulatory element (FSE) and the ribosome. Thus, our results revealed an unexpected role for eIF2A in modulating the translation of specific RNAs independent of its previously described role during initiation.
Project description:Purpose: To generate gene expression profiles of inguinal white, epididymal white and interscapular brown adipocytes Methods: Translating ribosomal affinity purification (TRAP) using an adipocyte-specific cre in adult wildtype mice followed by RNA-Seq Results: Using an optimized data analysis workflow, we mapped about 30 million sequence reads per sample to the mouse genome (build mm9) using Tophat and assembled reads into transcripts using Cufflinks.
