Expression of mutated

Notch1 gene products. (A) RT-PCR was performed on RNA isolated from 2 tumors harboring 3′ proviral insertions in theNotch1 gene. Amplification products were only obtained if reverse transcriptase was present in the cDNA synthesis reactions (+RT). (B) Partial nucleotide sequences obtained on the RT-PCR products in panel A span the junctions of Notch1 and LTR U3 segments of the fusion transcripts as shown schematically above. Numbers indicate the Notch1 nucleotide at the site of fusion and are based on the sequence of the wild-type Notch1cDNA.