Figure 1.

The N terminus of E1A binds to Id-1H and Id-2H. (A) Functional domains and deletion mutants of E1A_12S. The N-terminal domain required for binding to some bHLH transcription factors and Id proteins is shown by a caret. The domain required for induction of wt p53-dependent apoptosis and E1A_12S mutants having a deletion in this domain are shown below. (B) GST fusion proteins were made by inserting the cDNAs into the multicloning site of pGEX-2TK in which the nucleotide sequence corresponding to amino acid sequence RRASV for the catalytic subunit of A kinase was placed between GST and the cloning site. The binding of these proteins to E1A was analyzed by Western blotting with ³²P-labeled GST-N-terminal-E1A fragment (1–36 amino acids) after denaturation and renaturation of the proteins in buffer containing 6 and 3 M guanidinium hydrochloride, respectively. (C) GST-Id-1H and GST-Id-2H were similarly probed with ³²P-labeled GST-E1A_Δ17–23aa and GST-E1A_Δ54–69aa.