Variation of LTR size in molecular clones of the BALB/c endogenous ecotropic molecular leukemia virus
Retrovirus replication involves the synthesis of a DNA intermediate which integrates into the host cell genome. Structure analysis has revealed that the viral DNA contains a nucleotide sequence on both ends, termed long terminal repeat (LTR) which is derived from terminal sequences of the genomic RNA and consists of three portions: U3, R, and U5, representing respectively the 3' end, a short terminal repeated sequence, and the 5' end of the RNA. Each species of retrovirus has a characteristic length LTR; however, within a species different strains and isolates have variations in LTR size. The evolution of viral genomes during replication as an exogenous agent may involve changes which occur in the LTR. A population of molecular clones of an endogenous ecotropic virus was analyzed to identify possible changes which occur in the LTR region. Thirteen of fifteen plaque purified isolates examined have an insert which appears to be a typical viral genome with no major rearrangement or deletion. Six of these have an insert which contains a single LTR, and seven have an insert which contains two LTRs. Approximately half of the isolates, including single and double LTR clones, are infectious. More detailed analysis of plasmid subclones all containing double LTRs, revealed that the variation resided in the U3 region rather than the left LTR/right LTR junction region. Thus, the size variation of LTR in the WN1802N MuLV recombinant DNA clones appears to be different from the situation which is responsible for LTR size variability in some molecular clones of avian retrovirus. The mechanism which generates this diversity in the U3 region is not known. Perhaps there is a selective advantage for duplication/insertions in this region of the LTR. The SV40 repeat has an important activator role and it was postulated that repeats in retrovirus LTR have a similar role. (ERB)
- Research Organization:
- Oak Ridge National Lab., TN (USA); National Inst. of Environmental Health Sciences, Research Triangle Park, NC (USA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5175479
- Report Number(s):
- CONF-820439-5; ON: DE82017434
- Resource Relation:
- Conference: Symposium on genetics mechanisms of carcinogenesis, Gatlinburg, TN, USA, 11 Apr 1982
- Country of Publication:
- United States
- Language:
- English
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