One of the herpes simplex virus type 1 (HSV-1) true late gene products, Us11 protein, is brought into the cell by the infecting virion and may play a role in the virally-induced post-transcriptional control of gene expression. Us11 protein forms large oligomers, exhibits RNA binding features, concentrates into the nucleolus and is able to replace Rex protein in post-transcriptional control of human T-cell leukemia/lymphoma virus type I (HTLV-I) expression. As heat shock drastically alters protein synthesis, and because HSV-1 infection stimulates heat shock protein (Hsp) expression, we analyzed the consequence of heat shock in HeLa cells expressing Us11 alone, either transiently or constitutively. No detectable modification of the overall pattern of protein synthesis was observed in cells growing at normal temperatures, including no induction of Hsp expression or accumulation. However, Us11 protein expression induced an enhanced recovery of protein synthesis after heat shock. Moreover, the level of Us11 protein-mediated protection of protein synthesis was similar to that observed for cells made thermotolerant, but only when submitted to a mild heat shock. Finally, Us11 protein expression induced in cells an enhanced survival to heat shock.