Impact of the expression of human CTCF protein on the Saccharomyces cerevisiae genome

Abstract

In contrast to other eukaryotes, transcriptional regulation is particularly complex in animals, where it depends on long-range interactions between multiple distal enhancers and their target promoters. This is specially so in developmental genes, which usually have very complex expression patterns that require the control of many cis-regulatory elements. Thus, 3D chromatin organization is critical to guarantee proper cis-regulatory interactions and to avoid spurious ones. In different groups of animals, such as humans and other vertebrates, the protein CTCF works as an essential factor to control the 3D structure of the genome, regulating cohesinmediated chromatin interactions and the formation of loops between distal enhancers and their target promoters. In contrast, this type of long-range cis-regulation and its associated 3D chromatin organization have not been observed in other eukaryotic lineages such as plants and fungi. Interestingly, CTCF is also absent from the genome of these non-animal species. To investigate how CTCF can contribute to the establishment of long-range chromatin interactions in animals, we use the model organism Saccharomyces cerevisiae to study the effects that CTCF expression may have on the 3D organization of a fungal genome that does not have distal cis-regulation. We have successfully generated a yeast strain expressing human CTCF in which we have also introduced several transgenes of human-derived boundary elements containing CTCF binding sites. Using this model we are studying the ability of CTCF to establish 3D structures on the yeast chromatin, and its potential impact on the transcriptional regulation of this unicellular species.