Naslov
The Essential Human Cytomegalovirus Proteins pUL77 and pUL93 are Structural Components Necessary for Viral Genome Encapsidation

Autori
Borst, EM ; Bauerfeind, R ; Binz, A ; Stephan, T ; Neuber, S ; Wagner, K ; Steinbrück, L ; Sodeik, B ; Lenac Roviš, Tihana ; Jonjić, Stipan ; Messerle, M

Izvornik
Journal of virology (0022-538X) 90 (2016), 13; 5860-5875

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
human cytomegalovirus ; UL77 ; UL93 ; viral mutant ; capsid

Sažetak
Several essential viral proteins are proposed to participate in genome encapsidation of human cytomegalovirus (HCMV), among them pUL77 and pUL93, which remain largely uncharacterized. To gain insight into their properties, we generated an HCMV mutant expressing a pUL77-monomeric enhanced green fluorescent protein (mGFP) fusion protein and a pUL93-specific antibody. Immunoblotting demonstrated that both proteins are incorporated into capsids and virions. Conversely to data suggesting internal translation initiation sites within the UL93 open reading frame (ORF), we provide evidence that pUL93 synthesis commences at the first start codon. In infected cells, pUL77-mGFP was found in nuclear replication compartments and dot-like structures, colocalizing with capsid proteins. Immunogold labeling of nuclear capsids revealed that pUL77 is present on A, B, and C capsids. Pulldown of pUL77-mGFP revealed copurification of pUL93, indicating interaction between these proteins, which still occurred when capsid formation was prevented. Correct subnuclear distribution of pUL77-mGFP required pUL93 as well as the major capsid protein (and thus probably the presence of capsids), but not the tegument protein pp150 or the encapsidation protein pUL52, demonstrating that pUL77 nuclear targeting occurs independently of the formation of DNA-filled capsids. When pUL77 or pUL93 was missing, generation of unit-length genomes was not observed, and only empty B capsids were produced. Taken together, these results show that pUL77 and pUL93 are capsid constituents needed for HCMV genome encapsidation. Therefore, the task of pUL77 seems to differ from that of its alphaherpesvirus orthologue pUL25, which exerts its function subsequent to genome cleavage-packaging.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

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