“…It has been demonstrated that this region is preferentially sensitive to Si nuclease (2), prefers to bind gene 32 protein of bacteriophage T4 (33), reacts preferentially with carbodiimides (7), and is hypersensitive to micrococcal nuclease (Pommier et al, unpublished results). In addition, minor DNase I and DNase II hypersensitive sites reside at or near this region in SV40 minichromosomes (13,42). Whether the SV40 MAR has a cis-acting effect on the biological functions of the virus is a key question remaining to be answered, particularly since in studies to be reported elsewhere, the K gene MAR has been shown to exert a positive quantitative effect on gene expression (Blasquez et al and Xu et al, in press).…”