Ssdp proteins bind to LIM-interacting co-factors and regulate the activity of LIM-homeodomain protein complexes in vivo.
LIM-homeodomain transcription factors control a variety of developmental processes, and are assembled into functional complexes with the LIM-binding co-factor Ldb1 (in mouse) or Chip (in Drosophila). We describe the identification and characterization of members of the Ssdp family of proteins, which we show to interact with Ldb1 and Chip. The N terminus of Ssdp is highly conserved among species and binds a highly conserved domain within Ldb1/Chip that is distinct from the domains required for LIM binding and self-dimerization. In Drosophila, Ssdp is expressed in the developing nervous system and imaginal tissues, and it is capable of modifying the in vivo activity of complexes comprised of Chip and the LIM-homeodomain protein Apterous. Null mutations of the ssdp gene are cell-lethal in clones of cells within the developing wing disc. However, clones mutant for a hypomorphic allele give rise to ectopic margins, wing outgrowth and cell identity defects similar to those produced by mutant clones of Chip or apterous. Ssdp and Ldb/Chip each show structural similarity to two Arabidopsis proteins that cooperate with one another to regulate gene expression during flower development, suggesting that the molecular interactions between Ssdp and Ldb/Chip proteins are evolutionarily ancient and supply a fundamental function in the regulated control of transcription.
van Meyel
Donald J
DJ
The Salk Institute for Biological Studies, PO Box 85800, San Diego, CA 92186, USA.
Thomas
John B
JB
Agulnick
Alan D
AD
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000196:embryology / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D060588:LIM Domain Proteins; D060850:LIM-Homeodomain Proteins; D051379:Mice; D009154:Mutation; D009420:Nervous System / Q000196:embryology; D009687:Nuclear Proteins / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014921:Wings, Animal / Q000002:abnormalities / Q000196:embryology
C108740:Chi protein, Drosophila; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D060588:LIM Domain Proteins; D060850:LIM-Homeodomain Proteins; C102084:Ldb1 protein, mouse; D009687:Nuclear Proteins; C504092:Ssbp2 protein, mouse; C504093:Ssbp3 protein, mouse; D014157:Transcription Factors; C074459:ap protein, Drosophila