Nucleoprotein complexes from simian virus 40-infected monkey cells: Association of viral DNA with histones and the major viral structural protein

Abstract

Nucleoprotein complexes containing progeny SV40 DNA were isolated at 48 hr postinfection from infected permissive cells incubated in normal growth medium ( +), in growth medium lacking arginine (Arg −), and in normal growth medium containing 5-bromodeoxyuridine (BrdU +) and characterized. Virus production in both Arg − and Brdu + cells is markedly inhibited. The complexes were purified by two successive sucrose gradient sedimentations to remove cellular proteins and then by sedimentation onto a cushion of saturated KBr solution to remove contaminating virus and empty capsids. The complexes extracted from Arg +, Arg −, and BrdU + cells were found to have the same sedimentation coefficient of 57 S and the same density of 1.43 g/cm 3 after glutaraldehyde fixation and to contain supercoiled SV40 DNA. The major protein species of the complex are histones and the major viral capsid protein (VP1). The Arg + complex contains predominately histones, whereas the BrdU + complex contains predominately the major capsid protein. The Arg − complex contains substantial amounts of both histones and the major capsid protein. Complexes were also isolated from Arg + cells at different times (24, 34, and 48 hr) after infection and characterized. More VPl, relative to histones, was found in the complex isolated at early than at late time after infection. Thus, the BrdU + and Arg − complexes may represent complexes formed at different times in a lytic infection.