Cell-specificity of the chicken ovalbumin and conalbumin promoters

Abstract

A series of recombinant plasmids containing increasing lengths of the 5'-flanking promoter sequences of the chicken conalbumin and ovalbumin genes fused to the sequences coding for the SV40 T-antigen have been constructed. These recombinants were introduced into a variety of established cell lines and primary cultured cells by nuclear microinjection. Promoter activity was estimated by monitoring T-antigen synthesis by indirect immunofluorescence. We show that the microinjected ovalbumin and conalbumin promoter regions do not function in chicken fibroblasts, kidney cells and in a variety of non-chicken cells, irrespective of the presence of steroid hormone receptors. In contrast, these promoter regions are active in primary cultured chicken embryonic hepatocytes and oviduct tubular gland cells, suggesting the presence of cell-specific transcription factors in these cells. Unexpectedly, promoter sequences close to the TATA boxes of both the ovalbumin and conalbumin genes are sufficient to confer cell-specific expression. Most of the controls exerted on the ovalbumin and conalbumin promoters in the whole animal appear to be reproduced in vitro by nuclear microinjection of the chimeric genes into the primary cultured cells. However, the microinjected ovalbumin promoter is active in embryonic hepatocytes and thus escapes the regulation imposed on the corresponding inactive endogenous gene.