Proteasomal selection of multiprotein complexes recruited by LIM homeodomain transcription factors
Program in Gene Function and Expression; Program in Molecular Medicine
Cells, Cultured; Homeodomain Proteins; Models, Biological; Multiprotein Complexes; Proteasome Endopeptidase Complex; Recombinant Fusion Proteins; Signal Transduction; Transcription Factors; Transfection
Life Sciences | Medicine and Health Sciences
Complexes composed of multiple proteins regulate most cellular functions. However, our knowledge about the molecular mechanisms governing the assembly and dynamics of these complexes in cells remains limited. The in vivo activity of LIM homeodomain (LIM-HD) proteins, a class of transcription factors that regulates neuronal development, depends on the high-affinity association of their LIM domains with cofactor of LIM homeodomain proteins (LIM-HDs) (CLIM, also known as Ldb or NLI). CLIM cofactors recruit single-stranded DNA-binding protein 1 (SSDP1, also known as SSBP3), and this interaction is important for the activation of the LIM-HD/CLIM protein complex in vivo. Here, we identify a cascade of specific protein interactions that protect LIM-HD multiprotein complexes from proteasomal degradation. In this cascade, CLIM stabilizes LIM-HDs, and SSDP1 stabilizes CLIM. Furthermore, we show that stabilizing cofactors prevent binding of ubiquitin ligases to multiple protein interaction domains in LIM-HD recruited protein complexes. Together, our results indicate a combinatorial code that selects specific multiprotein complexes via proteasomal degradation in cells with broad implications for the assembly and specificity of multiprotein complexes.
Rights and Permissions
Citation: Proc Natl Acad Sci U S A. 2007 Sep 18;104(38):15000-5. Epub 2007 Sep 11. Link to article on publisher's site