Insufficient levels of NFIII and its low affinity for the origin of adenovirus type 12 (Ad12) DNA replication contribute to the abortive infection of BHK21 hamster cells by Ad12

Abstract

Human adenovirus type 12 (Ad12) induces undifferentiated sarcomas in neonate Syrian hamsters and hence presents a suitable model for studies of the molecular mechanism of viral oncogenesis. Since we submit that an understanding of the early steps in the interaction between Ad12 and hamster cells might shed light on the initiation of malignant transformation, the abortive infection of BHK21 hamster cells with Ad12 has been investigated in detail. Ad12 replication in these cells is blocked in early stages, while Ad2 can replicate to moderate titers. Early Ad12 genes are expressed in BHK21 hamster cells, but there is a total block in Ad12 DNA replication and late gene transcription. The Ad5-transformed hamster cell line BHK297-C131, with the left terminus of Ad5 DNA chromosomally integrated and constitutively expressed, allows limited levels of Ad12 DNA replication and late transcription, probably through Ad5 E1 functions, but not the translation of late Ad12 gene products. We have now investigated the capacities of binding of nuclear proteins NFI and NFIII from permissive human KB cells, nonpermissive hamster BHK21 cells, and complementing BHK297-C131 cells to the origin of replication (ori) of Ad2 or Ad12 DNA. The electrophoretic mobility shift assay has been used to assess these binding reactions. The data support the notions that NFIII of BHK21 cells has a lower affinity for the ori of Ad12 DNA than for the ori of Ad2 DNA and that the levels of NFIII in BHK21 cells are markedly reduced compared with the levels in the permissive human KB cells or the complementing BHK297-C131 hamster cells. These deficiencies are contributing factors for the abortive infection of BHK21 hamster cells with Ad12. The lack of sufficient levels of NFIII in BHK21 cells is also consistent with the decreased replication capacity of Ad2 in hamster compared with human cell lines.