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Cloning and nucleotide sequences of cDNAs spanning the splice junctions of Rous sarcoma virus mRNAs
Abstract:
The cDNAs corresponding to the 5' ends of the mRNAs coding for the envelope protein precursor (gPr92env) of the B77 strain and the transforming protein (pp60src) of the Prague B strain of Rous sarcoma virus were cloned into pBR322, and the nucleotide sequences surrounding the splice junctions were determined. Both mRNAs are products of single splicing events from a common donor splice site at nucleotide 398 from the 5' end of the RNA to acceptor splice sites at nucleotides 5078 and 7054 for the env and src mRNAs, respectively. These results confirm and extend previous conclusions based on peptide mapping and single-strand nuclease mapping. Compared with the sequence of the Prague C genome RNA, the B77 strain contains a 6-nucleotide deletion in the sequence corresponding to the hydrophobic portion of the signal peptide of the envelope protein precursor.
Insights
Researchers determined the nucleotide sequences of Rous sarcoma virus mRNAs for envelope protein precursor (gPr92env) and transforming protein (pp60src). They identified common splice sites and a deletion in the B77 strain, confirming previous findings.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Rous sarcoma virus (RSV) is a retrovirus known to cause tumors in chickens.
- Understanding the genetic structure and expression of viral proteins is crucial for comprehending viral oncogenesis.
Purpose of the Study:
- To determine the nucleotide sequences surrounding the splice junctions of the envelope protein precursor (gPr92env) and transforming protein (pp60src) mRNAs from RSV strains B77 and Prague B.
- To compare the genetic sequences of different RSV strains and identify potential variations impacting viral protein function.
Main Methods:
- Cloning of complementary DNAs (cDNAs) into the pBR322 plasmid.
- Determination of nucleotide sequences around splice junctions using sequencing techniques.
- Comparison of sequences with existing RSV genome RNA data.
Main Results:
- Both env and src mRNAs originate from single splicing events utilizing a common donor splice site.
- Specific acceptor splice sites were identified for env (nucleotide 5078) and src (nucleotide 7054) mRNAs.
- The B77 strain exhibits a 6-nucleotide deletion in the hydrophobic region of the envelope protein precursor's signal peptide compared to the Prague C strain.
Conclusions:
- The findings confirm and extend previous studies on RSV gene expression and splicing mechanisms.
- The identified deletion in the B77 strain suggests sequence variation that may influence envelope protein function or viral infectivity.