Characterization of the promoter of the Brugia malayi 12 kDa small subunit ribosomal protein (RPS12) gene

Unravelling gene regulatory mechanisms in human filarial parasites will require an understanding of their basic promoter structure. Only a single promoter from a human filarial parasite has been characterised in detail, the 70 kDa heat shock promoter of Brugia malayi (BmHSP70). This promoter was found to lack features found in a typical eukaryotic promoter. To determine if this was unique to the BmHSP70 promoter, a detailed analysis was undertaken of the promoter for the B. malayi small subunit 12 kDa ribosomal protein (BmRPS12) gene. The BmRPS12 promoter contained a unique tandem repeat structure. Deletion of these repeats resulted in the loss of 80% of promoter activity. Block replacement mutagenesis identified five regions outside the repeat which were essential for promoter activity. No predicted binding sites for proteins that normally associate with the typical eukaryotic core promoter domains were found in the essential domains or the repeat region. However, the repeat region contained many putative binding sites for GATAA transcription factor family proteins. Of 20 upstream domains of other ribosomal protein genes, one contained a repeat structure similar to that found in the BmRPS12 promoter, and the majority encoded putative GATAA transcription factor binding sites. This study demonstrates that the BmRPS12 promoter, like the BmHSP70 promoter, is distinct from a typical eukaryotic promoter.