The carboxyl terminus of the human cytomegalovirus UL37 immediate-early glycoprotein is conserved in primary strains and is important for transactivation

• Published in: Journal of general virology 2001-07, Vol.82 (7), p.1569-1579
• Main Authors: Hayajneh, Wail A, Contopoulos-Ioannidis, Despina G, Lesperance, Marci M, Venegas, Ana M, Colberg-Poley, Anamaris M
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Cell Line; Chloramphenicol O-Acetyltransferase; Cytomegalovirus - genetics; Cytomegalovirus - metabolism; Endoplasmic Reticulum - metabolism; Genetic Variation; Glycoproteins - genetics; Glycoproteins - metabolism; HSP70 Heat-Shock Proteins - genetics; Human cytomegalovirus; Humans; Immediate-Early Proteins - genetics; Immediate-Early Proteins - metabolism; Mitochondria - metabolism; Molecular Sequence Data; Mutation; Open Reading Frames; Phylogeny; Promoter Regions, Genetic; Transcriptional Activation; Transfection; UL37 protein; Viral Proteins - genetics; Viral Proteins - metabolism
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/0022-1317-82-7-1569

Center for Virology, Immunology and Infectious Disease Research, Children’s Research Institute 1 , Department of Infectious Diseases 2 and Department of Otolaryngology 3 , Children’s National Medical Center, George Washington University School of Medicine and Health Sciences, 111 Michigan Avenue, NW, Washington, DC 20010, USA Author for correspondence: Anamaris Colberg-Poley. Fax [phone]. e-mail acolberg{at}cnmc.org The human cytomegalovirus (HCMV) UL37 exon 3 (UL37x3) open reading frame (ORF) encodes the carboxyl termini of two immediate-early glycoproteins (gpUL37 and gpUL37 M ). UL37x3 homologous sequences are not required for mouse cytomegalovirus (MCMV) growth in vitro ; yet, they are important for MCMV growth and pathogenesis in vivo. Similarly, UL37x3 sequences are dispensable for HCMV growth in culture, but their requirement for HCMV growth in vivo is not known. To determine this requirement, we directly sequenced the complete UL37x3 gene in multiple HCMV primary strains. A total of 63 of the 310 amino acids in the UL37x3 ORF differ non-conservatively in one or more HCMV primary strains. The HCMV UL37x3 genetic diversity is non-random: the N -glycosylation (46/186 aa) and basic (9/15 aa) domains have the highest proportion of non-conservative variant amino acids. Nonetheless, most (15/17 signals) of the N- glycosylation signals are retained in all HCMV primary strains. Moreover, new N -glycosylation signals are encoded by 5/20 primary strains. In sharp contrast, the UL37x3 transmembrane (TM) ORF completely lacks diversity in all 20 HCMV sequenced primary strains, and only 1 of 28 cytosolic tail residues differs non-conservatively. To test the functional significance of the conserved carboxyl terminus, gpUL37 mutants lacking the TM and/or cytosolic tail were tested for transactivating activity. The gpUL37 carboxyl-terminal mutants are partially defective in hsp70 promoter transactivation even though they trafficked similarly to the wild-type protein into the endoplasmic reticulum and to mitochondria. From these results, we conclude that N -glycosylated gpUL37, particularly its TM and cytosolic domains, is important for HCMV growth in humans.