Transcriptional regulation of the Bombyx mori A3 cytoplasmic actin promoter in insect and mammalian cells

In this study we have analyzed the activity of the silkworm A3 cytoplasmic actin promoter in homologous insect and heterologous mammalian expression systems. To study the expression of the A3 actin promoter in insect cells we have isolated and characterized a stably transformed Bombyx mori cell line containing a novel selectable marker gene, puromycin N-acetyl transferase under control of transcriptional regulatory signals from the A3 cytoplasmic actin gene. Integration of the transfected plasmids into the host genome was demonstrated by Southern and in situ hybridizations. By using this cell line we have identified alternative transcriptional initiation sites for the A3 cytoplasmic actin gene. One of these start sites is located ;The regulatory elements of the A3 actin 5;Here we also report that A3 cytoplasmic actin based vectors can express foreign genes in various vertebrate cells. Using an A3 actin based expression cassette we have isolated stably transformed mammalian cell lines. Isolation of transformed cells was based on expression of the selected marker gene. Stable integration of A3 actin plasmid construct into the host genome was demonstrated. The integrated plasmid molecules frequently exhibited amplification which may indicate the presence of amplification promoting elements in the 5...