Distribution of G + C-rich regions in varicella-zoster virus DNA

The distribution of G + C-rich sequences in the genome of varicella-zoster virus (VZV) was investigated by partial denaturation, equilibrium sedimentation and Southern blot analysis. Portions of the IR(S) and TR(S) repeat sequences bounding the U(S) region of the DNA were found to have a G + C content 10 to 20% greater than the overall 47% G + C content of the VZV genome. A stretch of DNA (approx. 1500 base pairs) at the U(L)-IR(S) junction and repeated at the terminus of the TR(S) sequences was found to be about 64% G + C, based on sedimentation equilibrium measurements. We also report the cloning of a novel fragment containing sequences from both the U(L) and TR(S) termini of the VZV genome. Our ability to clone this fragment suggests that unusual forms of VZV DNA including closed circular molecules and molecules with an inverted U(L) region can be packaged into nucleocapsids.