Biological and molecular studies of endogenous retrovirus-like genes in Chinese hamster cell lines.

Two types of endogenous retroviral-like sequences related to type C or Intracisternal A Particle (IAP) genes respectively were detected in the Chinese hamster (CH) genome. Their structure and expression were analysed by virological and molecular approaches in different CH cell lines. Several clones were isolated from a CHO genomic library by screening--in stringent conditions--with type C (Gross-MuLV) or IAP (pMIA1) specific probes. These clones were further characterized by restriction mapping and sequencing. Transcripts of type C and IAP-like retroviral sequences were revealed either by PCR or by Northern blot analysis and hybridization with the respective specific probes. However only a few retroviral-like type C particles and no IA particles were detectable by electron microscopy. Only weak activation of type C viral production by halogenated pyrimidines or other classical viral activation agents was observed. No replication of this virus could be obtained in rodent, canine, simian or human cell lines.