The equine herpesvirus 1 UL11 gene product localizes to the trans-golgi network and is involved in cell-to-cell spread

Abstract

Experiments were conducted to identify and characterize the equine herpesvirus type 1 (EHV-1) UL11 homologous protein. At early-late times after EHV-1 infection of Rk13 cells several proteins at an M(r) of 8000 to 12,000 were detected using a UL11 protein-specific antiserum. Particularly, an M(r) of 11,000 protein was found abundantly in purified virions and could be assigned to the tegument fraction. As demonstrated by confocal laser scanning microscopy, UL11 reactivity localized predominantly to the trans-Golgi network of infected cells, but was also noted at the plasma membrane, specifically of transfected cells. Deletion of UL11 sequences in EHV-1 vaccine strain RacH (Hdelta11) and in the virulent isolate RacL22 (Ldelta11) resulted in viruses that were able to replicate on noncomplementing cells. It was shown in one-step growth kinetics on Rk13 cells that the reduction of intracellular and of extracellular virus titers caused by the absence of UL11 expression in either virus was somewhat variable, but approximately 10- to 20-fold. In contrast, a marked influence on the plaque phenotype was noted, as mean maximal diameters of plaques were reduced to 23.2% (RacL22) or 34.7% (RacH) of parental virus plaques and as an effect on the ability of RacH to cause syncytia upon infection was noted. It was therefore concluded that the EHV-1 UL11 product is not essential for virus replication in Rk13 cells but is involved in cell-to-cell spread.

Role of tegument proteins in herpesvirus assembly and egress

“…In HCMV, the pUL11 homolog pUL99 has been found to interact with the pUL16 homolog pUL94 (Liu et al, 2009). Consistent with the previously described model of capsid transport and budding, herpesviruses lacking pUL16, pUL21 or pUL11 (or their homologs) have defects in virus egress, resulting in decreased amounts of extracellular viruses produced and the accumulation of non-enveloped capsids in the cytoplasm (MacLean et al, 1989(MacLean et al, , 1992Baines and Roizman, 1992;Baines et al, 1994;Kopp et al, 2003;Schimmer and Neubauer, 2003;Silva et al, 2003;Britt et al, 2004;Jones and Lee, 2004;Silva et al, 2005;Seo and Britt, 2006;Guo et al, 2009).…”

The Protein Encoded by the U S 3 Orthologue of Marek's Disease Virus Is Required for Efficient De-Envelopment of Perinuclear Virions and Involved in Actin Stress Fiber Breakdown

“…The function of the U L 11 product on the early stages of HSV-1 egress is unclear. While the pseudorabies virus (PRV) and equine herpesvirus type 1 homologues appear to act in a later step of virus morphogenesis in the cytoplasm (18,38), an HSV-1 U L 11 mutant virus was characterized by an accumulation of nucleocapsids in the nucleus, juxtaposed to the inner lamella of the nuclear membrane. In addition, the number of particles in the cytoplasm was increased (1,22).…”

Binding Partners for the UL11 Tegument Protein of Herpes Simplex Virus Type 1

“…Like other alphaherpesvirus homologs, HSV-1 UL11 is thought to play a role in nucleocapsid envelopment and egress; however, the specific functions of this protein are unknown (3,21,25,35). Consistent with a role in budding at cytoplasmic locations, UL11 localizes primarily to the Golgi apparatus when expressed in the absence of other viral proteins (5).…”