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Transduction of c-src coding and intron sequences by a transformation-defective deletion mutant of Rous sarcoma virus
Abstract:
The mechanism of cellular src (c-src) transduction by a transformation-defective deletion mutant, td109, of Rous sarcoma virus was studied by sequence analysis of the recombinational junctions in three td109-derived recovered sarcoma viruses (rASVs). Our results show that two rASVs have been generated by recombination between td109 and c-src at the region between exons 1 and 2 defined previously. Significant homology between td109 and c-src sequences was present at the sites of recombination. The viral and c-src sequence junction of the third rASV was formed by splicing a cryptic donor site at the 5' region of env of td109 to exon 1 of c-src. Various lengths of c-src internal intron 1 sequences were incorporated into all three rASV genomes, which resulted from activation of potential splice donor and acceptor sites. The incorporated intron 1 sequences were absent in the c-src mRNA, excluding its being the precursor for recombination with td109 and implying that initial recombinations most likely took place at the DNA level. A potential splice acceptor site within the incorporated intron 1 sequences in two rASVs was activated and was used for the src mRNA synthesis in infected cells. The normal env mRNA splice acceptor site was used for src mRNA synthesis for the third rASV.
Insights
Recombination between Rous sarcoma virus (RSV) deletion mutant td109 and cellular src (c-src) DNA generated recovered sarcoma viruses (rASVs). These rASVs incorporated intron sequences, indicating recombination occurred at the DNA level, not via c-src mRNA.
Area of Science:
- Molecular Virology
- Cancer Biology
- Retroviral Oncogenesis
Background:
- Cellular src (c-src) is a proto-oncogene implicated in cell growth and differentiation.
- Rous sarcoma virus (RSV) contains the v-src oncogene, derived from c-src, causing cancer.
- Transformation-defective mutants, like td109, provide insights into oncogene activation mechanisms.
Purpose of the Study:
- To elucidate the mechanism of c-src transduction by the RSV deletion mutant td109.
- To characterize the genetic events leading to the formation of recovered sarcoma viruses (rASVs).
- To determine the molecular basis of src oncogene reactivation in td109-derived viruses.
Main Methods:
- Sequence analysis of recombinational junctions in three td109-derived rASVs.
- Comparison of viral and c-src sequences at recombination sites.
- Identification of splice donor and acceptor sites involved in viral genome formation.
Main Results:
- Two rASVs resulted from recombination between td109 and c-src between exons 1 and 2, with sequence homology at junctions.
- A third rASV formed via splicing of a cryptic donor site in td109's env region to c-src exon 1.
- All rASVs incorporated varying lengths of c-src intron 1, suggesting DNA-level recombination and activation of novel splice sites.
Conclusions:
- Initial recombination between td109 and c-src occurred at the DNA level, not through c-src mRNA.
- Incorporated intron sequences were utilized for src mRNA synthesis via activated splice sites.
- The study reveals complex mechanisms of oncogene复活 and recombination in retroviruses.