@article{mbs:/content/journal/jgv/10.1099/0022-1317-83-5-1013, author = "Marschall, Manfred and Stein-Gerlach, Matthias and Freitag, Martina and Kupfer, Regina and van den Bogaard, Miriam and Stamminger, Thomas", title = "Direct targeting of human cytomegalovirus protein kinase pUL97 by kinase inhibitors is a novel principle for antiviral therapy", journal= "Journal of General Virology", year = "2002", volume = "83", number = "5", pages = "1013-1023", doi = "https://doi.org/10.1099/0022-1317-83-5-1013", url = "https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-83-5-1013", publisher = "Microbiology Society", issn = "1465-2099", type = "Journal Article", abstract = "The protein kinase pUL97, encoded by human cytomegalovirus (HCMV), is an important determinant of virus replication. Recently, indolocarbazoles were identified as a class of substances that inhibit the pUL97 kinase activity in vitro. In parallel, it was shown that indolocarbazoles interfere with HCMV replication; however, the causal relationship between inhibition of pUL97 kinase activity and virus replication has not been clarified. Here evidence is provided that indolocarbazole-mediated inhibition of virus replication is a direct result of diminished pUL97 protein kinase activity. In cell culture infections, a strong and selective antiviral activity was measured with respect to several strains of HCMV in contrast with other related or non-related viruses. For fine quantification, recombinant HCMVs expressing green fluorescent protein were used, demonstrating the high sensitivity towards compounds NGIC-I and Gö6976. Interestingly, a ganciclovir-resistant virus mutant (UL97-M460I) showed increased sensitivity to both compounds. Supporting this concept, transfection experiments with cloned pUL97 revealed that ganciclovir-resistant mutants were characterized by reduced levels of autophosphorylation compared with wild-type and possessed particularly high sensitivity to indolocarbazoles. Moreover, the Epstein–Barr virus-encoded homologous kinase, BGLF4, which showed a similar pattern of autophosphorylation and ganciclovir phosphorylation activities, was not inhibited. Importantly, a cytomegalovirus deletion mutant, lacking a functional UL97 gene and showing a severe impairment of replication, was completely insensitive to indolocarbazoles. Thus, our findings indicate that a specific block in the activity of pUL97 is the critical step in indolocarbazole-mediated inhibition of virus replication and that pUL97 might be targeted very efficiently by a novel antiviral therapy.", }