Human parainfluenza virus type 3: messenger RNAs, polypeptide coding assignments, intergenic sequences, and genetic...

Area of Science:

• Virology
• Molecular Biology
• Genomics

Background:

• Human parainfluenza virus type 3 (PF3) is a significant respiratory pathogen.
• Previous research had identified cDNA clones for several PF3 mRNAs, including those for the hemagglutinin-neuraminidase glycoprotein (HN) and fusion glycoprotein (F).

Purpose of the Study:

• To identify and characterize the complete set of PF3 viral genes and their organization on the viral RNA (vRNA).
• To elucidate the gene order, intergenic regions, and gene-termination signals of PF3.
• To investigate potential readthrough transcription events.

Main Methods:

• Hybrid arrest and hybrid selection of in vitro translation were used to identify cDNA clones for nucleocapsid protein (NP), P+C, and matrix protein (M) mRNAs.
• Synthetic oligonucleotides and dideoxynucleotide sequencing were employed to analyze gene junctions in PF3 genomic RNA (vRNA).
• Oligonucleotide hybridization to separated intracellular PF3 mRNAs identified the sixth viral gene (L).

Main Results:

• Six unique PF3 mRNAs were identified, encoding seven proteins: NP, P, C, M, F, HN, and L.
• The gene order on the vRNA was established as 3'-NP-P+C-M-F-HN-L-5'.
• Intergenic regions contained the trinucleotide 3'-GAA, and genes initiated with conserved gene-start and terminated with conserved gene-end sequences, with an aberrant termination signal in the M gene.

Conclusions:

• The complete gene content and organization of PF3 were elucidated.
• The findings provide insights into PF3 gene expression regulation, including transcription initiation, termination, and potential readthrough.
• A close evolutionary relationship between PF3 and Sendai viruses was suggested.