cis-acting element in promoter and its binding factors play central role in gene expression. We characterized the promoter region of the
unc-18 gene, one of neuronal genes, by deletion analyses and identified the minimal regulatory 19-base element between -341 to -359. By screening the expression library, we identified factors binding to the 19-base element. One of these, the F09G2.9 gene product, is a member of the high mobility group(HMG) family of proteins.<Br> F09G2.9(RNAi) treatment caused reduction of the
unc-18 gene expression, suggesting that F09G2.9 positively regulates the
unc-18 gene expression. C. elegans shows chemotaxis to NaCl but avoids NaCl when they are kept under the starved condition with NaCl. However, F09G2.9(RNAi) animals showed chemotaxis toward NaCl irrespective of the conditioning. A F09G2.9::GFP promoter fusion with 0.7 kb of upstream sequence was expressed in head neurons, ventral nerve cord and tail neurons, whose expression pattern was similar to that of UNC-18::GFP. A recombinant C-terminal fragment in the F09G2.9 product containing HMG domain could bind to the 19-base element in
unc-18 promoter. Its in vivo binding to the 19-base element was also confirmed by the chromatin immunoprecipitation(ChIP) assay.<Br> To identify genes other than
unc-18 regulated by F09G2.9, we searched with the ChIP method. We cloned 14 genes containing binding site within 2 kb upstream from the ATG start codon. The F09G2.9 gene had the binding site in its promoter. Of genes detected, we especially noticed Y53C10A.5 gene encoding ubiquitin-conjugating enzyme and kallmann syndrome related gene, K03D10.1. Because both genes are implicated in neural functions. We are characterizing expression patterns of these genes by constructing GFP fusion proteins and observing phenotypes of these gene mutants. <Br> To further explore the role of the F09G2.9 gene in neural function, we are trying to isolate the deletion mutant with a PCR-based screening approach.