Abstract
Transvection, the functional interaction between homologous alleles, was first described in Drosophila in the 1950's. While transvection has been documented in a growing list of genes, using mutant alleles or synthetic constructs, in Drosophila and other organisms, the extent of its relevance to gene expression in physiological conditions has remained questionable. The molecular mechanisms underlying transvection are still largely unexplored, although hints suggest a link with the general machinery that controls the genome organization in the nucleus. In this review, we discuss recent results establishing the relevance of transvection for proper gene regulation, and in particular for the sexually dimorphic regulation of the Drosophila X-linked gene yellow. We also discuss the role that DNA insulator sequences and chromatin architectural proteins play in bringing in proximity homologous alleles, and how they may contribute to interallelic gene regulation.
Highlights
The organization of the genome inside the nucleus is central to gene regulation
We discuss the role that DNA insulator sequences and chromatin architectural proteins play in bringing in proximity homologous alleles, and how they may contribute to interallelic gene regulation
The first case of interallelic interaction was reported by Ed Lewis in 1954 when he studied the regulation of the Hox gene Ultrabithorax (Ubx) in the fruitfly Drosophila melanogaster (D. melanogaster)
Summary
The chromatin fiber is organized hierarchically, with most of the enhancergene promoter loops occurring in cis within selfinteracting domains called Topologically Associating Domains (TADs). These TADs are further organized into active or repressed compartments of interactions. This is the case, for instance, in Tcells, where physical interactions occur between the promoter of the IFN-γ gene, located on chromosome 10, and the regulatory region of the TH 2 cytokine locus, located on chromosome 11 [5] This interaction contributes to the regulation of cytokine expression in T cells and IFN-γ production in response to viral infection. The aforementioned examples illustrate a specific class of interactions between nonhomologous regions of the genome and that have been reviewed recently in Maass et al [3]
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