Constructing and Analyzing Fusion Promoter of Partial Sericin 1 and Bombyx A3 Cytoplasmic Actin

Previous report showed that the 209 bp DNA sequence upstream of the sericin 1 transcriptional start site （-586 to -378 bp） is involved in promoting transcription and responsible for the tissue specificity of sericin 1 promoter in silkworm Bombyx mori. In the present study, this 209 bp sequence exhibited enhancive effect by assembling in two different locations of ubiquitous Bombyx A3 cytoplasmic actin promoter. Sf-9 cells were transfected with recombinant plasmids using Cellfectin reagent. Firefly luciferase gene located downstream of fusion promoter was considered as a reporter, whereas the activity of the co-transfected Renilla luciferase gene （pGL2-SV40） provides an internal control. This 209 bp region up-regulates the strength of A3 promoter significantly （P〈0.01） when it enters into A3 promoter with respect to the position in sericin 1 gene promoter. This 209-bp fragment was almost functionless when being located upstream of A3 promoter.