Absence of circularly permuted and largely redundant sequences in the genome of visna virus.

A previous study of the infectivity of visna virus proviral DNA suggested that the genetic information of the virus is distributed over at least two of the RNA subunits. Because the genetic complexity of visna virus corresponds to the size of one subunit, this result may imply that sequence redundancies exist within each subunit. In the present article we have examined this question by constructing a map of the large RNase T1-resistant oligonucleotides of the viral genome. Our principal results are as follows: (i) all 36S RNA subunits have the same genetic content regardless of their polyadenylic acid [poly(A)] content; (ii) the poly(A) tract is present at the 3' end of the molecule; and (iii) the recoveries of 19 large RNase T1-resistant oligonucleotides from poly(A)-tagged RNA fragments of various sizes demonstrate that the oligonucleotides are organized in the same linear order within all subunits. Our results, therefore, exclude the existence of large sequence redundancies in the genome of visna virus.