Abstract |
Enhancers are regulatory elements that work primarily in cis. However, cases have been
found where they take part in trans interactions, and one of them is transvection.
Transvection is a phenomenon which, by taking advantage of the homologous pairing in
somatic cells of Diptera, leads to the transcriptional regulation of a gene by enhancers and
other regulatory sequences located in the homologous chromosome (in trans). Studies have
shown that the GYI insulator can mediate transvection by pairing with its copy in the
homologous chromosome. In this study we wanted to further study the correlation between
insulators and transvection. First, we tested the efficiency of GYI-mediated transvection
across the genome using a combination of two plasmid constructs with GYI which had been
proven to cause transvection in the attp2 and attp40 site by previous studies. With the
introduction of this combination in four more attP sites, we concluded that the GYI insulator
can indeed cause robust transvection throughout the genome. Then we studied the
contribution of GYI in ectopic expression of the reporter genes from neighbouring
enhancers. We found that GYI can, at the same time, cause transvection and affect ectopic
expression, either negatively or positively. Finally, we studied the putative involvement of
other insulators, besides GYI, in transvection. For this purpose we made a two-reporter
construct flanking one insulator and paired it with a two-enhancer construct flanking the
same insulator. Specifically we worked with the insulators Fab-8 and scs'. These experiments
showed that the insulator Fab-8 can cause strong transvection while scs' weak. Interestingly,
we found that each of the two enhancers can only activate one of the reporters, indicating
that transvection has directionality.
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