A cis-regulatory element promoting increased transcription at low temperature in cultured ectothermic Drosophila cells

Cells of many ectothermic species, including Drosophila melanogaster, maintain homeostatic function within a considerable temperature range. The cellular mechanisms enabling temperature acclimation are still poorly understood. At the transcriptional level, the heat shock response has been extensively analyzed. The opposite has received less attention. Here, using cultured Drosophila cells, we have identified genes with increased transcript levels at the lower end of the readily tolerated temperature range, as well as chromatin regions with increased DNA accessibility. Candidate cis-regulatory elements (CREs) for transcriptional upregulation at low temperature were selected and evaluated with a novel reporter assay for accurate assessment of their temperature-dependency. Robust transcriptional upregulation at low temperature could be demonstrated for a fragment from the pastrel gene, which expresses more transcript and protein at reduced temperatures. The CRE is controlled by the JAK/STAT signaling pathway and antagonizing activities of the transcription factors Pointed and Ets97D.