The Senegalese Sole Mx gene promoter contains a variable microsatellite region involved in the transcriptional

THE SENEGALESE SOLE Mx GENE PROMOTER CONTAINS A VARIABLE MICROSATELLITE REGION INVOLVED IN THE TRANSCRIPTIONAL CONTROL D. Alvarez-Torres*, L.P. Vieytes, E. Garcia-Rosado, M.C. Alonso and J. Bejar Universidad de Málaga, Málaga, Spain Interferons (IFNs) play a key role in the fish innate immune system against viral infections by stimulating the expression of IFN stimulated genes (ISGs), such as Mx. The mechanisms involved in the transcriptional regulation of fish ISGs are poorly understood. The sequencing of the Senegalese sole (Solea senegalensis) Mx gene (SsMx) promoter revealed the presence of a guanosine-citosine (G-C) rich region that contains a microsatellite, sited close to the translation start codon. The aim of the current study has been to determine the functional role of this region and to study its variability. In order to fulfill the first objective, RTG-2 cells were transiently transfected with a vector containing the luciferase reporter gene under the control of the wild type SsMx promoter or the mutated promoter in which the G-C region was removed. Afterwards, transfected cells were treated with poly I:C and the luciferase activity was measured at different times post-stimulation. The results indicated that this region is involved in the SsMx transcriptional control, being an essential motif for the SsMx promoter activity. In addition, the microsatellite variability was studied in different sole populations, in which four different alleles have been found. The differences in the genetic structure of this locus among these populations have been analyzed. Microsatellites in gene promoters are commonly involved in the transcriptional regulation, and allelic differences are frequently related to the promoter activation level. For this reason, it is tempting to suggest that the polymorphisms found in the G-C microsatellite of the SsMx promoter, which has not been previously described in any teleost Mx gene promoter, might have a functional meaning. However, further studies are required in order to establish a functional relationship between the different alleles and the level of SsMx transcription. In this approach, it would be mostly interesting to evaluate if this variability is related to the Senegalese sole resistance to viral infections. If such relationship exists, this locus could be used as a marker for genetic selection of this fish species. This study has been funded by the P09-CVI-4579 project, from Junta de Andalucía (Proyectos de Excelencia de la Junta de Andalucía).