Table 3.
Viral infections may induce or block SG formation. SGs may assemble as a defense against certain viruses, to limit the infection by sequestration and/or cleavage of translation factors, proteins and transcripts required for viral replication, and SG assembly apparently involves eIF2alpha phosphorylation [80], [195], [196], [197], [201], [202], [205], [206]. However, a number of DNA and RNA viruses block SG formation, and infected cells exposed to oxidative or ER-stress fail to aggregate SGs [196], [198], [199], [200], [204]. The 3′(−) end of flaviviruses and certain viral proteins bind TIAR and TIA1, thus inhibiting SG formation [198]. SGs can contribute positively to viral replication, by sequestration of antiviral proteins and mRNAs, or by nucleation of core particles and viral RNA, thus helping viral factories [201], [202]. Translation of alphavirus transcripts occurs in the presence of SGs and phosphorylated eIF2alpha, thanks to an adaptation called translation enhancer element [196]. Poliovirus infection triggers the formation of SGs that gradually loss PABP, G3BP and eIF4G, which are cleaved during the first hours of the viral cycle. Whether SG formation helps or inhibits poliovirus replication is unknown [80], [197], [207].
| Virus | eIF2alpha phosphorylation | SG induction (marker) | SG inhibition (stressor; marker) | References | |
|---|---|---|---|---|---|
| Positive stranded RNA | Mouse hepatitis Coronavirus | Yes | Yes (TIAR) | Unknown | [195] |
| Semliki Forest Virus | Yes | Yes (TIA-1, TIAR, eIF3) | Yes (arsenite; TIA-1) | [196] | |
| Poliovirus | Unknown | Yes (TIA-1, polyA+ mRNA, Sam68, G3BP, eIF4G, PABP) | No (heat shock; Sam68, Hsp27) | [80], [197] | |
| West Nile and Dengue virus | No | No (TIAR) | Yes (arsenite; TIAR) | [198] | |
| HIV-1 | No | No (PABP1, Staufen1) | Yes (arsenite; PABP1, Staufen1) | [199] | |
| Double stranded RNA | Rotavirus (Reoviridae) | Yes | No (TIA-1, eIF4E, S6, PABP) | Yes (arsenite; TIA-1, eIF4E, S6) | [200] |
| Reoviridae | Yes | Yes (TIA-1, TIAR, G3BP, eIF4G, eIF4E, eIF3, 7F4) | Unknown | [201], [202] | |
| DNA | Herpex Simplex virus 1 | Unknown | No (TIA1/R) | Unknown | [203] |
| Human Cytomegalovirus | Unknown | No (eIF4G) | Yes (thapsigargin; eIF4G) | [204] |