STABLE TRANSFER AND RESTRICTED EXPRESSION OF A CLONED CLASS-I GENE ENCODING A SECRETED TRANSPLANTATION-LIKE ANTIGEN

The identification of a unique [mouse] major histocompatibility complex class I gene, designated Q10, which encodes a secreted rather than a cell surface antigen has led to questions regarding its potential role in regulating immunological functions. Since the Q10 gene is specifically activated only in the liver, the molecular mechanisms which control its expression should be defined in a tissue-specific fashion. Results obtained by transfection of the cloned Q10 gene, either in the absence or presence of a heterologous transcriptional enhancer, into a variety of cell types of different tissue derivations are consistent with the Q10 gene being regulated at 2 levels. The 1st is by a cis-dependent mechanism which appears to involve site-specific DNA methylation. The 2nd is by a trans-acting mechanism which would include the possibility of an enhancer binding factor. The ability to efficiently express the Q10 gene in certain transfected cell lines offers an opportunity to obtain this secreted class I antigen in quantities sufficient for functional studies; this should also make it possible to define regulatory sequences which may be responsible for the tissue-specific expression of Q10.