a “coiled-coil” motif is important for oligomerization and dna binding properties of human cytomegalovirus protein ul77u201c卷曲螺旋u201d主题对寡聚化和dna结合特性很重要ul77人类巨细胞病毒的蛋白质.pdf

A ‘‘Coiled-Coil’’ Motif Is Important for Oligomerization and DNA Binding Properties of Human Cytomegalovirus Protein UL77 . ´ ¨ . ¤ Christina Sylvia Meissner , Panja Koppen-Rung , Alexandra Dittmer , Sara Lapp, Elke Bogner* ´ ¨ Institute of Virology, Charite Universitatsmedizin Berlin, Berlin, Germany Abstract Human cytomegalovirus (HCMV) UL77 gene encodes the essential protein UL77, its function is characterized in the present study. Immunoprecipitation identified monomeric and oligomeric pUL77 in HCMV infected cells. Immunostaining of purified virions and subviral fractions showed that pUL77 is a structural protein associated with capsids. In silico analysis revealed the presence of a coiled-coil motif (CCM) at the N-terminus of pUL77. Chemical cross-linking of either wild-type pUL77 or CCM deletion mutant (pUL77DCCM) implicated that CCM is critical for oligomerization of pUL77. Furthermore, co- immunoprecipitations of infected and transfected cells demonstrated that pUL77 interacts with the capsid-associated DNA packaging motor components, pUL56 and pUL104, as well as the major capsid protein. The ability of pUL77 to bind dsDNA was shown by an in vitro assay. Binding to certain DNA was further confirmed by an assay using biotinylated 36-, 250-, 500-, 1000-meric dsDNA and 966-meric HCMV-specific dsDNA designed for this study. The binding efficiency (BE) was determined by image processing program defining values above 1.0 as positive. While the BE of the pUL56 binding to the 36-mer bio- pac1 containing a packaging signal was 10.060.63, the one for pUL77 was only 0.2 60.03. In contrast to this observation the BE of pUL77 binding to bio-500 bp or bio-1000 bp was 2.260.41 and 4.9 60.71,