As shown in Figure 1B, only those constructs which include the entire putative activation domain were able to activate transcription from the A1 promoter. P1-231 was not able to activate in spite of the fact that it contains about two thirds of the acidic region. These results suggest that residues in the region between amino acids 231 and 321 are essential for P1 activity, and that residues C-terminal to 321 can be deleted without a significant loss in P1 activity. Figure 1 . Various truncations made of the P1 gene, outside of the Myb domain in the C-terminal region.
Numbers indicate amino acid termination points of each truncation.
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