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RNA editing in the phosphoprotein gene of the human parainfluenza virus type 3
M S Galinski1, R M Troy, A K Banerjee
1Department of Molecular Biology, Cleveland Clinic Foundation, Ohio 44195.
Abstract:
RNA editing of the human parainfluenza virus type 3 (HPIV3) phosphoprotein (P) gene was found to occur for the accession of an alternate discontinuous cistron. Editing occurred within a purine-rich sequence (AAUUAAAAAAGGGGG) found at the mRNA nucleotides 791-805. This sequence resembles an HPIV3 consensus transcription termination sequence and is located at the 5'-end of the putative D protein coding sequences. Editing at an alternate site (AAUUGGAAAGGAAAGG), mRNA nucleotides 1121-1136, for accession of a conserved V cistron, which is present in a number of paramyxovirus P genes, was not found to occur in HPIV3. In contrast with many other paramyxoviruses, editing was indiscriminate with the insertion of 1-12 additional G residues not present in the gene template. RNA editing was found to occur in both in vivo (HPIV3 infected cells) and in vitro (purified nucleocapsid complexes) synthesized mRNAs. Further, the in vitro prepared mRNA was edited regardless of whether the nucleocapsid complexes were transcribed in the presence or absence of uninfected human lung carcinoma (HLC) cell lysates. These results support the notion that RNA editing appears to be exclusively a function of viral proteins.
Insights
RNA editing in human parainfluenza virus type 3 (HPIV3) occurs within the phosphoprotein (P) gene, inserting extra G residues. This process appears to be solely a function of viral proteins, not host cell factors.
Area of Science:
- Molecular Virology
- RNA Biology
Background:
- Human parainfluenza virus type 3 (HPIV3) is a significant respiratory pathogen.
- RNA editing is a post-transcriptional modification process observed in some RNA viruses.
Purpose of the Study:
- To investigate the mechanism and characteristics of RNA editing in the HPIV3 phosphoprotein (P) gene.
- To determine the role of host factors in HPIV3 RNA editing.
Main Methods:
- Analysis of HPIV3 P gene mRNA sequences from infected cells (in vivo) and purified nucleocapsid complexes (in vitro).
- Comparison of edited and unedited mRNA sequences to identify editing sites and patterns.
- In vitro transcription assays using purified HPIV3 nucleocapsid complexes with and without cell lysates.
Main Results:
- HPIV3 P gene RNA editing occurs within a purine-rich sequence (nucleotides 791-805), facilitating the accession of an alternate discontinuous cistron.
- Editing involves the indiscriminate insertion of 1-12 additional G residues, unlike the conserved V cistron editing seen in other paramyxoviruses.
- RNA editing was observed in both in vivo and in vitro synthesized mRNAs.
- In vitro editing occurred irrespective of the presence of human lung carcinoma (HLC) cell lysates, suggesting host factors are not required.
Conclusions:
- HPIV3 RNA editing is an intrinsic viral process, primarily occurring within the P gene.
- The editing mechanism is distinct from other paramyxoviruses and involves non-templated G insertions.
- Viral proteins are exclusively responsible for HPIV3 RNA editing, independent of host cell machinery.