Transvection is an epigenetic phenomenon wherein regulatory elements communicate between different chromosomes in , and is thereby dependent upon the three-dimensional organization of the genome. Transvection is best understood in , where homologous chromosomes are closely paired in most somatic nuclei, although similar phenomena have been observed in other species. Previous data have supported that the genome is generally permissive to enhancer action in , a form of transvection where an enhancer on one homolog activates gene expression from a promoter on a paired homolog. However, the capacity of different genomic positions to influence the quantitative output of transvection has yet to be addressed. To inve... More
Transvection is an epigenetic phenomenon wherein regulatory elements communicate between different chromosomes in , and is thereby dependent upon the three-dimensional organization of the genome. Transvection is best understood in , where homologous chromosomes are closely paired in most somatic nuclei, although similar phenomena have been observed in other species. Previous data have supported that the genome is generally permissive to enhancer action in , a form of transvection where an enhancer on one homolog activates gene expression from a promoter on a paired homolog. However, the capacity of different genomic positions to influence the quantitative output of transvection has yet to be addressed. To investigate this question, we employed a transgenic system that assesses and compares enhancer action in and in at defined chromosomal locations. Using the strong synthetic eye-specific enhancer , we show that loci supporting strong -expression tend to support robust enhancer action in , whereas locations with weaker -expression show reduced transvection in a fluorescent reporter assay. Our subsequent analysis is consistent with a model wherein the chromatin state of the transgenic insertion site is a primary determinant of the degree to which enhancer action in will be supported, whereas other factors such as locus-specific variation in somatic homolog pairing are of less importance in influencing position effects on transvection.
