Kinetic studies of the effect of a 17-nucleotide difference in the 0.3-kb region containing the R- U5-5′ leader sequence of Friend murine leukemia virus on viral gene expression.

ABSTRACT In addition to the env gene, a 0.3-kb fragment containing the R-U5-5′ leader sequence is essential for the induction of spongiform neurodegeneration by Friend murine leukemia virus (Fr-MLV) clone A8 and it also influences expression of the Env protein. Kinetic studies were carried out using two recombinant viruses, R7f, carrying the A8 0.3-kb fragment, and Rec5, carrying the 0.3-kb fragment of the non-neuropathogenic Fr-MLV clone 57. These analyses suggested that the 0.3-kb fragment influenced the expression level of the Env protein by regulating the amount of spliced env-mRNA rather than the amount of total viral mRNA or viral production. [ABSTRACT FROM AUTHOR]