DNA PACKAGING BY L1 AND L2 CAPSID PROTEINS OF BOVINE PAPILLOMAVIRUS TYPE-1

Encapsidation of circular DNA by papillomavirus capsid protein was inv estigated in Cos-1 cells. Plasmids carrying both an SV40 origin of rep lication (or) and an E. coli on were introduced into Cos-1 cells by DN A transfection. PV capsid proteins were supplied in trans by recombina nt vaccinia viruses. Pseudovirions were purified from infected cells a nd their packaged DNA was extracted and used to transform E. coil as a n indication of packaging efficacy. VLPs assembled from BPV-1 L1 alone packaged little plasmid DNA, whereas VLPs assembled from BPV-1 L1+L2 packaged plasmid DNA at least 50 times more effectively. BPV-1 L1+L2 V LPs packaged a plasmid containing BPV-1 sequence 8.2 +/- 3.1 times mor e effectively than a plasmid without BW sequences. Using a series of p lasmid constructs comprising a core BPV-1 sequence and spacer DNA it w as demonstrated that BW VLPs could accommodate a maximum of about 10.2 kb of plasmid DNA, and that longer closed circular DNA was truncated to produce less dense virions with shorter plasmid sequences. The pres ent study suggests that packaging of genome within PV virions involves interaction of L2 protein with specific DNA sequences, and demonstrat es that PV pseudovirions have the potential to be used as DNA delivery vectors for plasmids of up to 10.2 kb. (C) 1998 Academic Press.