The protein encoded by the Drosophila position-effect variegation suppressor gene Su(var)3-9 combines domains of antagonistic regulators of homeotic gene complexes

EMBO J. 1994 Aug 15;13(16):3822-31.


Modifier mutations of position-effect variegation (PEV) represent a useful tool for a genetic and molecular dissection of genes connected with chromatin regulation in Drosophila. The Su(var)3-9 gene belongs to the group of haplo suppressor loci which manifest a triplo enhancer effect. Mutations show a strong suppressor effect even in the presence of PEV enhancer mutations, indicating a central role of this gene in the regulation of PEV. By molecular analysis, Su(var)3-9 could be correlated with a 2.4 kb transcript which encodes a putative protein of 635 amino acids containing a chromo domain and a region of homology to Enhancer of zeste and trithorax, two antagonistic regulators of the Antennapedia and Bithorax gene complexes, as well as to the human protein ALL-1/Hrx which is implicated in acute leukemias. This region of homology is found in all four proteins at the C-terminus. The homology of Su(var)3-9 to both negative (Polycomb and Enhancer of zeste) and positive (trithorax) regulators of the Antennapedia and Bithorax complexes also suggests similarities in the molecular processes connected with stable transmission of a determined state and the clonal propagation of heterochromatinization.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cloning, Molecular
  • DNA Transposable Elements
  • DNA-Binding Proteins / genetics
  • Drosophila / genetics*
  • Drosophila Proteins*
  • Gene Expression Regulation*
  • Gene Rearrangement
  • Genes, Homeobox / genetics
  • Genes, Insect / genetics*
  • Genes, Regulator / genetics
  • Genes, Suppressor / genetics*
  • Genomic Library
  • Male
  • Molecular Sequence Data
  • Nuclear Proteins*
  • Ocular Physiological Phenomena
  • Polycomb Repressive Complex 2
  • Proteins / genetics
  • Repressor Proteins / genetics*
  • Sequence Homology, Amino Acid
  • Transcription Factors*
  • Transcription, Genetic
  • Transformation, Genetic


  • DNA Transposable Elements
  • DNA-Binding Proteins
  • Drosophila Proteins
  • Nuclear Proteins
  • Proteins
  • Repressor Proteins
  • Su(var)3-9 protein, Drosophila
  • Transcription Factors
  • Trl protein, Drosophila
  • E(z) protein, Drosophila
  • Polycomb Repressive Complex 2

Associated data

  • GENBANK/X80069
  • GENBANK/X80070