Transcriptome screening identifies TIPARP as an antiviral host factor against the Getah virus.

Alphaviruses are emerging and re-emerging viruses that cause severe disease and threaten public health worldwide. To advance the understanding of the underlying mechanisms of alphavirus replication and identify new host restriction factors, we performed RNA-seq and identified antiviral host factors on the Getah virus (GETV), a re-emerging alphavirus. We identified tetrachlorodibenzo-p-dioxin-inducible poly(ADP ribose) polymerase (TIPARP) as a host antiviral factor. TIPARP is downregulated in GETV-infected Vero cells, and its overexpression significantly inhibits GETV replication, while TIPARP deficiency results in significantly increased viral titers. We demonstrated that TIPARP interacts with the viral E2 glycoprotein, inducing k48-linked ubiquitination and subsequent proteasomal degradation. Additionally, we found that TIPARP recruits the E3 ubiquitin ligase membrane-associated RING-CH 8 (MARCH8) to modify the ubiquitination, leading to the degradation of E2. Lys253 in E2 was identified as the TIPARP-facilitated ubiquitination site. A mutation in Lys253 resulted in the loss of TIPARP's anti-GETV effect. Our study demonstrated for the first time that host TIPARP is a restricting factor against GETV replication. Investigating the underlying mechanisms and understanding TIPARP for GETV will be essential to fully understanding viral pathogenesis and developing novel broad-spectrum therapeutic strategies against alphavirus infection. IMPORTANCE Alphaviruses threaten public health continuously, and Getah virus (GETV) is a re-emerging alphavirus that can potentially infect humans. Approved antiviral drugs and vaccines against alphaviruses are few available, but several host antiviral factors have been reported. Here, we used GETV as a model of alphaviruses to screen for additional host factors. Tetrachlorodibenzo-p-dioxin-inducible poly(ADP ribose) polymerase was identified to inhibit GETV replication by inducing ubiquitination of the glycoprotein E2, causing its degradation by recruiting the E3 ubiquitin ligase membrane-associated RING-CH8 (MARCH8). Using GETV as a model virus, focusing on the relationship between viral structural proteins and host factors to screen antiviral host factors provides new insights for antiviral studies on alphaviruses.