Meeting Abstract

P1-37   -   Predicting hyperosmolality-inducible transcription factors using MEME tools Kim, C*; Kültz, D; University of California, Davis cshkim@ucdavis.edu

Transcriptional regulation is one of the major mechanisms by which organisms are able to adapt to fluctuating environments. This regulation is orchestrated by the interplay between cis-regulatory elements and trans-acting factors. Euryhaline tilapia (Oreochromis mossambicus) tolerate a wide range of salinity up to 3x seawater and thus, this species is an appropriate model to examine transcriptional regulation mechanisms in response to salinity stress. Using OmB cells (O. mossambicus brain cell line), targeted proteomics revealed 21 proteins that are transcriptionally up-regulated during salinity stress. Potential regulatory regions (including distant and proximal promoters and 5’ UTRs) from each corresponding gene were isolated to identify common binding sites for salinity-inducible transcription factors. The STREME motif searching tool was used to identify five ungapped motifs that are enriched in the regulatory sequences of all 21 hyperosmolality-responsive tilapia genes. These binding site motifs were analyzed using the TOMTOM and FIMO motif scanning tools. Among the five motifs, the top-ranked two statistically significant motifs were representing binding sites for Forkhead box protein L1 (FoxL1) and metal response element binding transcription factor 1 (Mtf1). The annotation of these two binding sites into 21 hyperosmolality-induced tilapia genes allowed us to experimentally validate two promising genes (chloride intracellular channel 2(clic2) and uridine phosphorylase 1(upp1)) enriched with these motifs in proximal promoters. GFP/RFP reporter assays showed clic2 and upp1 are transcriptionally induced by hyperosmolality and subsequent motif-mutagenesis (loss-of-function) revealed their transcriptional induction requires these motifs. Moreover, our results also rationalize FoxL1 and Mtf1 genetic manipulation experiments to investigate their involvement in the osmotic regulation of the 21 osmoresponsive genes. This study is funded by NSF-IOS 1656371 and BARD IS-5358-21.