Visualization of Transvection in Living Drosophila Embryos

Bomyi Lim, Tyler Heist, Michael Levine, Takashi Fukaya

Research output: Contribution to journalArticlepeer-review

105 Scopus citations


How remote enhancers interact with appropriate target genes persists as a central mystery in gene regulation. Here, we exploit the properties of transvection to explore enhancer-promoter communication between homologous chromosomes in living Drosophila embryos. We successfully visualized the activation of an MS2-tagged reporter gene by a defined developmental enhancer located in trans on the other homolog. This trans-homolog activation depends on insulator DNAs, which increase the stability—but not the frequency—of homolog pairing. A pair of heterotypic insulators failed to mediate transvection, raising the possibility that insulator specificity underlies the formation of chromosomal loop domains. Moreover, we found that a shared enhancer co-activates separate PP7 and MS2 reporter genes in cis and in trans. Transvecting alleles weakly compete with one another, raising the possibility that they share a common pool of the transcription machinery. We propose that transvecting alleles form a trans-homolog “hub,” which serves as a scaffold for the accumulation of transcription complexes. Lim et al. explore a process called transvection in living Drosophila embryos, whereby enhancers on one homolog activate transcription units on the other homolog. They show that insulators facilitate transvection by stabilizing allele-allele pairing. Surprisingly, a shared enhancer coactivates a cis-linked PP7 reporter gene along with a trans-linked MS2 reporter contained on the other homolog. This coactivation is consistent with emerging evidence for transcription “hubs” containing clusters of RNA polymerase II and associated activators.

Original languageEnglish (US)
Pages (from-to)287-296.e6
JournalMolecular Cell
Issue number2
StatePublished - Apr 19 2018

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Cell Biology


  • Drosophila embryos
  • TADs
  • chromosomal loop domains
  • enhancers
  • insulators
  • live imaging
  • transcription
  • transvection


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