CHIMERIC BK VIRUS-DNA EPISOMES IN A PAPILLARY UROTHELIAL BLADDER-CARCINOMA

BK virus (BKV) DNA sequences were identified in a papillary urothelial bladder carcinoma by Southern blot hybridization. The carcinoma conta ined both integrated and extrachromosomal DNA. Integrated sequences ha d a clonal restriction pattern, suggesting that BKV was integrated at some early stage of neoplastic initiation or progression. Viral episom es consisted of a population of covalent polymers based on a high-mole cular-weight DNA unit, about 11-12 kb in size. DNA sequences non-homol ogous to the BKV genome were encompassed within DNA episomes, suggesti ve of acquisition of cellular sequences by viral DNA replication at th e integration site. Extrachromosomal, chimeric DNA molecules were pres ent at an average level of about 50 copies per cell, but their size, a pparently incompatible with viral assembly, showed that BKV productive infection was impaired. The data suggest that infected cells underwen t reversible changes affecting autonomous BKV DNA replication.