Position effect variegation (PEV) is a perturbation of genes expression resulting from the changes in their chromatin organization due to the abnormal juxtaposition with heterochromatin. The exact molecular mechanisms of PEV remain enigmatic in spite of the long history of PEV studies. Here, we developed a genetic model consisting of PEV-inducing chromosome rearrangement and a reporter gene under control of the UAS regulatory element. Expression of the reporter gene could be regulated by adjustment of the GAL4 transactivator activity. Two UAS-based systems of expression control were tested - with thermosensitive GAL4 repressor GAL80 and GAL4-based artificial transactivator GeneSwitch. Both systems were able to regulate the expression of the UAS-controlled reporter gene over a wide range, but GAL80 repressed the reporter gene more efficiently. Measurements of the heterochromatin-mediated repression of the reporter gene in the GAL4+GAL80 system point to the existence of a threshold level of expression, above which no PEV is observed.
In(1)w
m4
has been known for decades as a classic example of a position effect variegation-causing rearrangement and has been mentioned in hundreds of publications. Nevertheless, its euchromatic breakpoint has not been localized with base-pair resolution. We performed nanopore sequencing of DNA from
In(1)w
m4
homozygous flies and determined the exact position of euchromatic (chrX:2767875) and heterochromatic breakpoints of the rearrangement. The heterochromatic breakpoint is located in an unlinked part of the genome in the region, enriched in TEs (transposable elements) fragments. A set of unique piRNAs could be detected in the region.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.