The human cytomegalovirus-specific UL1 gene encodes a late-phase glycoprotein incorporated in the virion envelope

J Virol. 2012 Apr;86(8):4091-101. doi: 10.1128/JVI.06291-11. Epub 2012 Feb 15.


We have investigated the previously uncharacterized human cytomegalovirus (HCMV) UL1 open reading frame (ORF), a member of the rapidly evolving HCMV RL11 family. UL1 is HCMV specific; the absence of UL1 in chimpanzee cytomegalovirus (CCMV) and sequence analysis studies suggest that UL1 may have originated by the duplication of an ancestor gene from the RL11-TRL cluster (TRL11, TRL12, and TRL13). Sequence similarity searches against human immunoglobulin (Ig)-containing proteins revealed that HCMV pUL1 shows significant similarity to the cellular carcinoembryonic antigen-related (CEA) protein family N-terminal Ig domain, which is responsible for CEA ligand recognition. Northern blot analysis revealed that UL1 is transcribed during the late phase of the viral replication cycle in both fibroblast-adapted and endotheliotropic strains of HCMV. We characterized the protein encoded by hemagglutinin (HA)-tagged UL1 in the AD169-derived HB5 background. UL1 is expressed as a 224-amino-acid type I transmembrane glycoprotein which becomes detectable at 48 h postinfection. In infected human fibroblasts, pUL1 colocalized at the cytoplasmic site of virion assembly and secondary envelopment together with TGN-46, a marker for the trans-Golgi network, and viral structural proteins, including the envelope glycoprotein gB and the tegument phosphoprotein pp28. Furthermore, analyses of highly purified AD169 UL1-HA epitope-tagged virions revealed that pUL1 is a novel constituent of the HCMV envelope. Importantly, the deletion of UL1 in HCMV TB40/E resulted in reduced growth in a cell type-specific manner, suggesting that pUL1 may be implicated in regulating HCMV cell tropism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Amino Acid Substitution
  • Capsid Proteins / metabolism
  • Cell Line
  • Cytomegalovirus / genetics*
  • Cytomegalovirus / metabolism*
  • Evolution, Molecular
  • Gene Deletion
  • Gene Expression Regulation, Viral
  • Gene Order
  • Genes, Viral
  • Glycoproteins / chemistry
  • Glycoproteins / genetics*
  • Glycoproteins / metabolism*
  • Humans
  • Kinetics
  • Molecular Sequence Data
  • Protein Binding
  • Protein Transport
  • Sequence Alignment
  • Transcription, Genetic
  • Viral Envelope Proteins / chemistry
  • Viral Envelope Proteins / genetics*
  • Viral Envelope Proteins / metabolism*
  • Virion / chemistry
  • Virion / metabolism*
  • Virus Assembly
  • Virus Replication


  • Capsid Proteins
  • Glycoproteins
  • Viral Envelope Proteins