Interactions of heterologous DNA with polyomavirus major structural protein, VPI

'Empty' polyomavirus pseudocapsids, self-assembled from the major structura l protein VP1, bind DNA nonspecifically and can deliver it into the nuclei of mammalian cells for expression [Forstova et al, (1995) Hum. Gene Ther, 6 , 297-306], Formation of suitable VP1-DNA complexes appears to be the limit ing step in this route of gene delivery. Here, the character of VP1-DNA int eractions has been studied in detail. Electron microscopy revealed that VP1 pseudocapsids can create in vitro at least two types of interactions with double-stranded DNA: (i) highly stable complexes, requiring free DNA ends, where the DNA is partially encapsidated; and, (il) weaker interactions of p seudocapsids with internal parts of the DNA chain. (C) 1999 Federation of E uropean Biochemical Societies.