SELF-ASSEMBLY OF THE JC VIRUS MAJOR CAPSID PROTEIN, VP1, EXPRESSED ININSECT CELLS

The major capsid protein of human polyomavirus JC virus, VP1, has been cloned into a baculovirus genome and expressed in insect cells. The V P1 protein was expressed in the cytoplasm and transported into the nuc leus. It was then purified by a sucrose cushion and CsCl density gradi ent centrifugation to near homogeneity, Electron microscopy showed tha t isolated recombinant VP1 protein self-assembled into a capsid-like s tructure similar to the natural empty capsid, Both chelator (EDTA) and reducing agent (DTT) are required to disrupt the capsid structure int o the pentameric capsomeres, as demonstrated by haemagglutination assa y and electron microscopy. These results suggest that JC virus VP1 can be transported into the nucleus and self-assembled to form capsid-lik e particles without the involvement of the viral minor capsid proteins , VP2 and VP3, In addition, metal ions and disulphide bonds appear to be important in maintaining the integrity of the viral capsid structur e.