FIG. 6.

PDX-1 physically interacts with tissue-specific bHLH proteins. (A) In vitro-translated, ³⁵S-labeled PDX-1 or Lmx1.1 protein was incubated with GST alone or with the GST-BETA2 bHLH domain (containing amino acids 94 to 162 of BETA2/NeuroD). Bound proteins were immobilized on glutathione-Sepharose beads and resolved by SDS-PAGE followed by autoradiography. Ten percent of the ³⁵S-labeled PDX-1 and Lmx1.1 proteins used in the binding assay were loaded in lanes 1 and 4, respectively. (B) ³⁵S-labeled full-length HLH proteins BETA2/NeuroD, Mash1, MyoD, and Id1 were tested as for panel A for interaction with GST–PDX-1. GST alone and GST fused to E47/Pan1 amino acids 510 to 647 (including the bHLH dimerization domain) were used as controls. (C) Ten percent of the ³⁵S-labeled HLH proteins used for the assay were resolved by SDS-PAGE.