Distal promoter of the Drosophila melanogaster cytoskeletal actin 5C (Act5C) gene, one of two alternative promoters that transcribe the gene from separate start sites (Bond and Davidson 1986). Drives strong constitutive expression, comparable to the induced Mtn promoter, in stably transfected Drosophila S2 cells (Angelichio et al. 1991).
Length: 2432 bp
Strength: strong
Tissue: Not tissue-restricted in culture. Active without induction in Drosophila S2 cells (Angelichio et al. 1991) and in the C2 (larval CNS-derived) and S2R+ (late embryo-derived) cell lines (Qin et al. 2010).
Expression: constitutive
Origin: Drosophila melanogaster Act5C gene, distal promoter fragment
Characteristics
The Act5C gene is transcribed from two alternative promoters — a distal promoter roughly 1.9 kb upstream of the exon-1 cap site and a weaker proximal promoter within about 450 bp of the exon-2 cap site (Bond and Davidson 1986). In stably transfected Drosophila S2 cells, a -2500 to +88 fragment of the distal promoter gives HIV-1 gp120 RNA and protein levels comparable to the copper-induced Mtn promoter and about three- to fivefold higher than the alpha1-tubulin promoter. Act5C constructs were kept at about threefold lower gene copy number than Mtn constructs, so the promoter may be stronger per copy (Angelichio et al. 1991). In transiently transfected Drosophila C2 and S2R+ cells it drives GFP slightly more strongly than the copia promoter (Qin et al. 2010).
Applications: Constitutive promoter for heterologous protein expression in stably transfected Drosophila S2 cells, shown with a secreted HIV-1 gp120 glycoprotein (Angelichio et al. 1991), and for transient GFP reporter expression in Drosophila S2R+ and C2 cells (Qin et al. 2010). Proposed for use together with the Mtn promoter in one cell line, so that a constitutively expressed RNA or protein can be studied against an inducibly expressed regulator (Angelichio et al. 1991).
Limitations: Stable S2 lines carrying Act5C constructs had about threefold lower gene copy number than Mtn lines, possibly because high copy numbers of constitutive promoters disadvantage the cells (Angelichio et al. 1991). The gene's proximal promoter, driven from the exon-2 cap site, is markedly weaker than the distal fragment, so promoter-fragment choice affects output (Bond and Davidson 1986).
Angelichio et al. (1991).
Comparison of several promoters and polyadenylation signals for use in heterologous gene expression in cultured Drosophila cells.
Nucleic Acids Res - Angelichio 1991 Drosophila Promoters
Qin et al. (2010).
Systematic Comparison of Constitutive Promoters and the Doxycycline-Inducible Promoter.
PLoS ONE - Qin 2010 Promoter Comparison
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