Simian virus 40 regulatory region structural diversity and the associationof viral archetypal regulatory regions with human brain tumors

The regulatory region (RR) of simian virus 40 (SV40) contains enhancer/prom oter elements and an origin of DNA replication. Natural SV40 isolates from simian brain or kidney tissues typically have an archetypal RR arrangement with a single 72-basepair enhancer element. A rare simpler shorter SV40 RR exists that Jacks a duplicated sequence in the G/C-rich region and is terme d protoarchetypal. Occasionally, SV40 strain variants arise de novo that ha ve complex RRs, which typically contain sequence reiterations, rearrangemen ts, and/or deletions. These variants replicate faster and to higher titers in tissue culture; we speculate that such faster-growing variants were sele cted when laboratory strains of SV40 were initially, recovered. SV40 strain s with archetypal RRs have been found in some human brain tumors. The possi ble implications of these findings and a brief review of the SV40 RR struct ure are presented.