Rubella virus cDNA. Sequence and expression of E1 envelope protein.

Area of Science:

• Virology
• Molecular Biology
• Protein Chemistry

Background:

• Rubella virus is an important human pathogen.
• Understanding rubella virus envelope proteins is crucial for vaccine development and antiviral strategies.
• Previous studies have characterized some rubella virus proteins, but detailed analysis of the E1 envelope protein and its precursor processing is ongoing.

Purpose of the Study:

• To isolate and characterize a cDNA clone encoding the rubella virus E1 and E2 envelope proteins.
• To determine the sequence and structural features of the E1 protein, including signal peptides and cleavage sites.
• To investigate potential homologies and functional domains of the E1 protein and assess its expression and antigenicity.

Main Methods:

• cDNA cloning and sequencing
• DNA sequence analysis
• Amino acid sequence deduction and comparison
• Expression in COS cells using a simian virus 40-derived vector

Main Results:

• A cDNA clone encoding the complete E1 (410 amino acids) and part of the E2 envelope proteins of rubella virus was isolated.
• Sequence analysis revealed a potential replicase or encapsidation recognition site and localized the E1/E2 cleavage site.
• The mature E1 protein is preceded by a 20-amino acid hydrophobic signal peptide with flanking protease cleavage sites, suggesting facilitated membrane translocation.
• The rubella virus E1 protein showed no significant homology to alphavirus E1 proteins but shared homology with bovine sperm histone (residues 262-300).
• The E1 protein was successfully expressed in COS cells and demonstrated antigenic similarity to the naturally expressed protein.

Conclusions:

• The characterized cDNA clone provides valuable genetic information for rubella virus E1 and E2 proteins.
• The identified signal peptide and cleavage sites offer insights into the processing and membrane targeting of the E1 protein.
• The unexpected homology to bovine sperm histone suggests potential novel functions or evolutionary relationships.
• Successful expression and antigenic similarity confirm the utility of the cDNA clone for further immunological studies and potential vaccine research.