Characterization of supercoiled nucleoprotein complexes released from detergent-treated vaccinia virions.

Treatment of vaccinia virions with 1% sodium dodecyl sulfate in the absence of reducing agents resulted in the release of subviral particles termed "subnucleoids," which contained viral DNA in combination with four polypeptides with molecular weights of 90,000, 68,000, 58,000 and 10,000. Biochemical and electron microscopic studies showed that viral DNA in combination with these polypeptides was maintained in a superhelical configuration. When subnucleoids were "fixed" with glutaraldehyde and formaldehyde and then examined by electron microscopy, spherical particles were observed, in which the supercoiled DNA was folded into globular structures that were 20 to 60 nm in diameter and were interconnected by DNA-protein fibers resembling the nucleosome structures described for eucaryotic chromatin.