Cis and trans interactions between the iab regulatory regions and abdominal-A and abdominal-B in Drosophila melanogaster

Genetics. 1995 Feb;139(2):835-48. doi: 10.1093/genetics/139.2.835.

Abstract

The infra-abdominal (iab) elements in the bithorax complex of Drosophila melanogaster regulate the transcription of the homeotic genes abdominal-A (abd-A) and Abdominal-B (Abd-B) in cis. Here we describe two unusual aspects of regulation by the iab elements, revealed by an analysis of an unexpected complementation between mutations in the Abd-B transcription unit and these regulatory regions. First, we find that iab-6 and iab-7 can regulate Abd-B in trans. This iab trans regulation is insensitive to chromosomal rearrangements that disrupt transvection effects at the nearby Ubx locus. In addition, we show that a transposed Abd-B transcription unit and promoter on the Y chromosome can be activated by iab elements located on the third chromosome. These results suggest that the iab regions can regulate their target promoter located at a distant site in the genome in a manner that is much less dependent on homologue pairing than other transvection effects. The iab regulatory regions may have a very strong affinity for the target promoter, allowing them to interact with each other despite the inhibitory effects of chromosomal rearrangements. Second, by generating abd-A mutations on rearrangement chromosomes that break in the iab-7 region, we show that these breaks induce the iab elements to switch their target promoter from Abd-B to abd-A. These two unusual aspects of iab regulation are related by the iab-7 breakpoint chromosomes that prevent iab elements from acting on Abd-B and allow them to act on abd-A. We propose that the iab-7 breaks prevent both iab trans regulation and target specificity by disrupting a mechanism that targets the iab regions to the Abd-B promoter.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • DNA-Binding Proteins / genetics
  • Drosophila Proteins*
  • Drosophila melanogaster / embryology
  • Drosophila melanogaster / genetics*
  • Enhancer Elements, Genetic / genetics
  • Female
  • Gene Expression Regulation, Developmental / genetics*
  • Gene Rearrangement
  • Genes, Homeobox / genetics
  • Genes, Insect / genetics
  • Genetic Complementation Test
  • Homeodomain Proteins*
  • Insect Hormones / genetics*
  • Male
  • Mutation / physiology
  • Nuclear Proteins*
  • Promoter Regions, Genetic / genetics
  • Proteins / genetics*
  • Regulatory Sequences, Nucleic Acid / genetics*
  • Thorax / growth & development
  • Transcription Factors*
  • Translocation, Genetic
  • Y Chromosome

Substances

  • Abd-B proteins, Drosophila
  • DNA-Binding Proteins
  • Drosophila Proteins
  • Homeodomain Proteins
  • Insect Hormones
  • Nuclear Proteins
  • Proteins
  • Transcription Factors
  • Ubx protein, Drosophila
  • abd-A protein, Drosophila