Identification of hypoxia response elements controlling the expression of the drosophila prolyl-4-hydroxylase gene fatiga, that operates as an oxygen sensor

ACEVEDO JM, CENTANIN L, DEKANTY A, WAPPNER P

Pinamar

Congreso; 41st Annual Meeting: Argentine Society for Biochemistry and Molecular Biology; 2005

HIF-1 is a heterodimeric α/β transcription factor essential for the adaptation of cells to reduced oxygen conditions. this heterodimer is present only in hypoxia to activate transcription of target genes by binding to hypoxia response elements (hres) in their regulatory regions. under normoxia hif-1α is degraded in the 26s proteasome, and the process depends on the hydroxylation of 2 key proline residues in HIF-1α polypeptide. hydroxylation is catalyzed by specific prolyl-4-hydroxylases (phds) that utilize o2 as a co-substrate thus, functioning as oxygen sensors. we had previously identified sima and fatiga (fga) as the drosophila homologues of hif-1α and the phd, respectively. we found that fga gene generates 3 different transcripts by a combination of alternative splicing and alternative initiation of transcription (fga a, b y c). fga b and c but not fga a are induced in hypoxia or upon over-expression of sima, originating a negative feed back loop. we have used luciferase reporter constructs in drosophila s2 cells to identify the hres responsible for the hypoxic induction of fga b and c. we found a regulatory region containing 6 putative hres that conferred sima dependent inducibility and site directed mutagenesis of these motifs led to the identification of one particular hre responsible for sima /hypoxia-dependent inducibility.