Disease relevance of MuHV1gpM99

• We have identified, characterized, and expressed in bacteria and recombinant vaccinia viruses a protein which likely represents the murine cytomegalovirus (MCMV) homologue of the human cytomegalovirus (HCMV) 28-kDa matrix phosphoprotein, the product of the HCMV UL99 open reading frame (ORF) [1].
• The cytotoxic T-lymphocyte (CTL) response against the murine cytomegalovirus (MCMV) immediate-early gene 1 (IE1) 89-kDa phosphoprotein pp89 plays a major role in protecting BALB/c mice against the lethal effects of the viral infection [2].
• We previously identified two open reading frames (ORFs) of murine cytomegalovirus (MCMV), M83 and M84, which are putative homologs of the human cytomegalovirus (HCMV) UL83 tegument phosphoprotein pp65 (L. D. Cranmer, C. L. Clark, C. S. Morello, H. E. Farrell, W. D. Rawlinson, and D. H. Spector, J. Virol. 70:7929-7939, 1996) [3].
• Similar to the HCMV and HHV-6 proteins, pp50 is predicted to have a hydrophilic C-terminus which contains a putative nuclear targeting sequence [4].

High impact information on MuHV1gpM99

• Recognition by cytolytic T lymphocytes of the phosphoprotein pp89, the immunodominant viral antigen expressed in the immediate-early phase of infection, was selectively prevented during the subsequent expression of viral early genes [5].
• Since neither rate of synthesis, amount, stability, nor nuclear transport of pp89 was modified, the failure in recognition indicates a selective interference with pp89 antigen processing and presentation [5].
• The murine cytomegalovirus (MCMV) immediate-early gene 1 (IE1) encodes an 89-kDa phosphoprotein (pp89) which plays a key role in protecting BALB/c mice against the lethal effects of the MCMV infection [6].
• The results suggest that the phosphoprotein pp89 stimulates cells to enter the cell cycle [7].
• All plasmid constructs that contained the intact coding sequences for pp89 induced gene expression in trans [8].

Biological context of MuHV1gpM99

• This region contains the immediate-early gene (gene ieI) which encodes pp89, a phosphoprotein active in transcriptional regulation [9].
• This allowed us to localize the partial pp50 transcript to a region between map coordinates 0.228 and 0.260 of the MCMV genome (Smith strain, Vancouver) [10].
• The coding sequence for the murine cytomegalovirus (MCMV) nonstructural phosphoprotein pp50 has previously been mapped to the EcoRI-L fragment of the viral genome [4].

Anatomical context of MuHV1gpM99

• Presence of AM3/pp50 mRNA, as well as IE-1 transcripts, was confirmed by reverse transcription-polymerase chain reaction in 3 of 5 latently infected spleens [11].
• During transient expression of pp50 in COS-1 cells, the phosphoprotein was readily detectable in the nuclei, indicating that it possesses a nuclear localization signal (NLS) [12].
• Similarly, during MCMV infection of Balb/3T3 fibroblasts, pp50 was present in the nuclei of infected cells between 8 and 24 hr postinfection, suggesting that the protein contains a functional nuclear targeting sequence [4].
• We have identified an abundant 50K phosphoprotein (pp50) in MCMV-infected 3T3-L1 cells and shown by immunofluorescence microscopy and surface-iodination experiments that pp50 is localized to the plasma membrane of the infected cell [10].

Associations of MuHV1gpM99 with chemical compounds

• Finally, results from our analysis by nonreducing and native gel electrophoresis, as well as fractionation by sucrose gradients suggested that pp50 expressed in the absence of viral infection can form disulfide-linked homopolymers [4].

Analytical, diagnostic and therapeutic context of MuHV1gpM99

• Immunoprecipitation with monoclonal antibody revealed that 31K to 67K polypeptides were related to pp89 [13].
• Low levels of the AM3/pp50 transcript were also detected in latently infected tissues by in situ hybridization [11].
• Immunofluorescence experiments with monoclonal antibodies specific for pp50 demonstrated that recombinant pp50 expressed transiently in COS-1 cells or during infection by recombinant Vaccinia virus was localized to the nucleus [4].
• Sequence analysis and expression of the murine cytomegalovirus phosphoprotein pp50, a homolog of the human cytomegalovirus UL44 gene product [4].

References