Analysis of the chimeric proteins. RT-PCR analysis ofETV6-ARG (A) and ARG-ETV6 (B) fusion products. Total RNA from the patient (lane 1) and 2 different healthy donor white blood cells (lanes 2 and 3) was used for RT-PCR with primers located in the relevant exons of ETV6 and ARG(see Materials and Methods). Marker sizes are indicated on the left. (A) RT-PCR analysis of ETV6-ARG. Two specific bands of 194 and 131 bp, respectively, were detected. The different PCR products are the result of an alternative splicing event in the ARGgene, as shown in (C). (B) RT-PCR analysis of ARG-ETV6. One specific band of 343 bp was detected. (C) Schematic representation of ETV6 (top) and ARG(IB) (bottom) cDNAs, 3′RACE clones (boxed), and predicted ETV6-ARG andARG-ETV6 fusion proteins. The vertical arrow indicates the breakpoint. The alternatively spliced hypothetical ARG exon is indicated. HLH, helix-loop-helix domain; ETS, ETS-family DNA binding domain; SH3, SH3 domain; PTK, protein-tyrosine kinase domain; pro rich, proline-rich domains. Full-length cDNAs from the ARG andETV6 genes are shown at the top and bottom, respectively. The 2 different types of 3′RACE-PCR clones are shown in the box. The nested PCR primers are indicated as arrows at the extremities of the RACE clones.