Conservation patterns of mouse “virus-like” (VL30) DNA sequences

Abstract

VL30 sequences are a murine dispersed multigene family with several “retrovirus-like” characteristics. Notably, they share basic structural features with retrovirus proviruses and 30S RNA transcripts of these genes are capable of efficient packaging in C-type virions and may be subsequently transmitted to other cells. It is not known whether VL30 information is genetically related to endogenous proviruses or to cellular elements. We extended our studies concerning evolutionary conservation and genetic relationships of VL30 sequences within and outside the genus Mus. The following observations were made: (i) Although VL30 DNA sequences were detected in all mice examined, analysis of VL30 reiteration disclosed up to a 100-fold difference among different Mus species. For example, only 1–3 VL30 copies were detected in M. pahari compared to approximately 200 VL30 copies in certain strains of M. musculus. (ii) Using low-stringency hybridization conditions, nucleotide sequences homologous to mouse VL30 DNA were detected in the DNAs of other animal cells such as rat and human. (iii) The cross-hybridization between mouse VL30 DNA and rat genomic DNA was fully accounted for by the cross-homology between the respective VL30 elements. The homologous regions were mapped and were found confined within a small fragment (<1kb) in both mouse VL30 and rat 30S DNA (as well as in Ha-MSV). The data suggested differential conservation of subsets of VL30 information. (iv) A subset of VL30 information was found in the mouse genome in molecular linkages other than “standard” VL30 units (that is a segment of VL30 DNA flanked by non-VL30 sequences). Results are discussed in terms of the possible evolution of VL30 sequences.