Human Cytomegalovirus UL47 Tegument Protein Functions after Entry and before Immediate-Early Gene Expression

Abstract

The human cytomegalovirus UL47 open reading frame encodes a 110-kDa protein that is a component of the virion tegument. We have constructed a cytomegalovirus mutant, ADsubUL47, in which the central portion of the UL47 open reading frame has been replaced by two marker genes. The mutant replicated to titers 100-fold lower than those for wild-type virus after infection at either a high or a low input multiplicity in primary human fibroblasts but was substantially complemented on cells expressing UL47 protein. A revertant virus in which the mutation was repaired, ADrevUL47, replicated with wild-type kinetics. Mutant virions lacked UL47 protein and contained reduced amounts of UL48 protein. The mutant was found to be less infectious than wild-type virus, and a defect very early in the replication cycle was observed. Transcription of the viral immediate-early 1 gene was delayed by 8 to 10 h. However, this delay was not the result of a defect in virus entry or of the inability of virion proteins to transactivate the major immediate-early promoter. We also show that the UL47 protein coprecipitated with the UL48 and UL69 tegument proteins and the UL86-encoded major capsid protein. We propose that a UL47-containing complex is involved in the release of viral DNA from the disassembling virus particle and that the loss of UL47 protein causes this process to be delayed.

Tegument Proteins of Human Cytomegalovirus

“…In addition to binding UL48, UL47 also interacts with the UL69 tegument protein and with the major capsid protein, perhaps forming a complex (14). Interestingly, the absence of UL47 results in a decrease in the accumulation of the UL48 protein (but apparently not the mRNA from which it is translated) and a decrease in UL48 incorporation into virions (14). This indicates that UL47 is required for either the efficient translation of or, more likely, the stability of UL48.…”

“…Disruption of the UL47 gene, which is expressed with late kinetics (69), results in a 100-fold reduction in viral titers after infections at either high or low multiplicities (14). The UL47 protein is found in approximately equal levels in infectious virions, NIEPS, and dense bodies (9).…”

“…UL47 binds to the high-molecular-weight protein (HMWP) (UL48) (see below) and, thus, has been called HMWP-binding protein (194). In addition to binding UL48, UL47 also interacts with the UL69 tegument protein and with the major capsid protein, perhaps forming a complex (14). Interestingly, the absence of UL47 results in a decrease in the accumulation of the UL48 protein (but apparently not the mRNA from which it is translated) and a decrease in UL48 incorporation into virions (14).…”

Host and Viral Proteins in the Virion of Kaposi's Sarcoma-Associated Herpesvirus

“…on May 10, 2018 by guest http://jvi.asm.org/ lacking the ORF63 homolog (UL47) exhibits an entry defect potentially at the step of capsid disassembly (4,13,33). Several chaperones have been found in the tegument of HCMV (66), another herpesviruses, and play critical roles in both cellular and viral processes.…”

Identification and Characterization of the Pseudorabies Virus Tegument Proteins UL46 and UL47: Role for UL47 in Virion Morphogenesis in the Cytoplasm

“…Then, remaining extracellular virus was inactivated by low-pH treatment. Cells and supernatants were harvested separately immediately thereafter (0 h), and after 4,8,12,24, and 36 h of incubation at 37°C. Virus progeny was titrated on RK13 cells.…”