Genomic organization and regulation of three cecropin genes in Anopheles gambiae.

Three cecropin genes (AgCecA-C) were identified from Anopheles gambiae, a major vector for malaria in sub-Saharan Africa. These genes form a cluster with AgCecA and AgCecB positioned in opposite orientation, while AgCecC is downstream of AgCecA in the same direction. One intron is present in each of these three genes. Motif searches of promoter regions revealed elements that could be regulated by the NF-kappaB family of transcriptional regulators. The divergent promoter (1186 nucleotides in length) between CecA and CecB and the promoter for CecC were analysed by transfection in An. gambiae cell lines. Results showed that these promoters were up-regulated by lipopolysaccharide. The activity was further elevated when heat-inactivated microbes were used to challenge the cell line. At least one NF-kappaB site was required for inducible expression of both CecA and CecB.