Studies have been conducted to evaluate the polynucleotide sequence homology between human papovaviruses JC and BK and SV40. JCV shares approximately 25% of its sequences with BKV and 11% with SV40. Experiments are also in progress to examine the relationship between BKV and SV40 tumor antigens and to characterize the structure, mode of synthesis and biological function of oligomeric forms of papovaviruses.