Characterization of the chicken L-Maf, MafB and c-Maf in crystallin gene regulation and lens differentiation

Genes Cells. 2002 Jul;7(7):693-706. doi: 10.1046/j.1365-2443.2002.00548.x.


Background: Members of the Maf family, including L-Maf, MafB and c-Maf, are "basic region/leucine zipper" (bZIP) transcription factors. Maf proteins contain a highly conserved acidic transactivation domain (AD), and a bZIP region that mediates DNA-binding activity. The hinge region between AD and bZIP varies considerably in length between different proteins. Recent studies reveal that L-Maf, c-Maf and MafB play key roles in vertebrate lens development.

Results: We investigated the transactivation activity of individual factors in culture cells to analyse their specific functions. In transient transfection assays with a reporter gene containing Maf responsive elements, MafB and c-Maf activated higher levels of the reporter gene than L-Maf. However, L-Maf transactivated the alphaA-crystallin promoter as effectively as MafB and c-Maf, and induced the expression of the endogenous delta-crystallin gene more efficiently than the other two proteins. Domain-swapping experiments reveal that the bZIP region of MafB takes part in strong transcriptional activity, while the acidic and hinge regions (AH) of c-Maf collectively serve as a strong transactivation domain. The AH region of L-Maf (but not c-Maf) conferred transactivation activity to induce delta-crystallin gene expression.

Conclusions: These results suggest that despite their similar DNA binding properties, L-Maf, MafB and c-Maf regulate different sets of target genes by complex interactions with multiple factors that recognize cis-elements in promoters. The AH region of L-Maf has a distinct role in inducing endogenous delta-crystallin gene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Animals
  • Avian Proteins*
  • Binding Sites
  • Chickens
  • Crystallins / genetics*
  • Crystallins / physiology
  • DNA / metabolism
  • DNA-Binding Proteins / physiology*
  • Gene Expression Regulation, Developmental*
  • Lens, Crystalline / embryology*
  • Lens, Crystalline / physiology
  • MafB Transcription Factor
  • Mice
  • Oncogene Proteins / physiology*
  • Promoter Regions, Genetic
  • Protein Binding
  • Proto-Oncogene Proteins / physiology*
  • Proto-Oncogene Proteins c-maf
  • Recombinant Proteins / genetics
  • Trans-Activators / physiology*
  • Transcription Factors*
  • Transcription, Genetic


  • Avian Proteins
  • Crystallins
  • DNA-Binding Proteins
  • Maf protein, mouse
  • MafB Transcription Factor
  • Mafb protein, mouse
  • Oncogene Proteins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-maf
  • Recombinant Proteins
  • Trans-Activators
  • Transcription Factors
  • DNA