Baiker, A, Maercker, C, Piechaczek, C, Schmidt, SB, Bode, J, Benham, C et al.. Mitotic stability of an episomal vector containing a human scaffold/matrix-attached region is provided by association with nuclear matrix. Nat Cell Biol 2: 182-184
DNA replication occurs in tight association with the nuclear matrix, where binding of the replication origin to the nuclear matrix must precede the onset of S phase. We have shown previously that the origin of replication of the simian virus 40 (SV40) genome linked to a human scaffold/matrix-attached region (S/MAR) allows sustained episomal replication (where an episome is autonomous, self-replicating DNA) that is independent of the expression of the virally encoded large T-antigen. A vector with this combination of SV40 origin and potential for matrix association is maintained in cultured cells for at least 100 cell generations, in the absence of selection. Here we show, by in situ hybridization and nuclear-fractionation procedures, that there is a specific interaction of this vector with the nuclear matrix and the chromosome scaffold, presumably through proteins that both structures have in common. This interaction correlates with replication of the vector as an episome. These observations allow a mechanistic explanation for the episomal replication and mitotic stability of this new type of vector.