Volume 18, no. 7, p. 4118-4130, 1998, and volume 19, no. 1, p. 594-601, 1999: Dr. Thomas B. Friedman and Thomas Barber from the National Institute on Deafness and Other Communication Disorders at the National Institutes of Health have alerted us that the cDNA clone of the Pax3-FKHR transcription factor used in experiments published in the Molecular and Cellular Biology articles listed above was incompletely described. As indicated in the Epstein et al. article, the plasmid encoding Pax3-FKHR is a mouse-human hybrid composed of murine Pax3 (GenBank accession no. X59358, nucleotides 313 to 719) encoding an amino acid sequence identical to that of human PAX3, followed by human PAX3-FKHR (GenBank accession no. U02368, nucleotides 471 to 2556), and a sequence encoding a 9-residue carboxy-terminal hemagglutinin (HA) epitope tag. The sequence of this HA tag (YDVPDYASL) differs from the common HA epitope (YPYDVPDYA) and corresponds to 9 residues of the 12-residue peptide used to raise commercially available anti-HA antibodies (Covance Research Products Inc., Richmond, Calif.). The YDVPDYASL tag is also recognized by the commercially available anti-HA antibodies.

Both the murine and human Pax3 full-length cDNAs contain three ATG codons in frame. We are not aware of any published or preliminary data describing the amino-terminal sequence of either Pax3 or PAX3-FKHR in vivo. If all three ATGs are used in vivo, either in normal development or in rhabdomyosarcoma, the proteins would differ by 10 or 11 amino-terminal residues. The chimeric cDNA used in our studies and in those of others (Fredericks et al., Mol. Cell. Biol. 15:1522-1535, 1995; Scheidler et al., Proc. Natl. Acad. Sci. USA 93:9805-9809, 1996) begins at the second ATG. To date, results from our laboratories independently confirm that the presence or absence of the first ATG codon or of the carboxy-terminal HA tag in the context of Pax3-FKHR does not alter the results and conclusions reported in our studies.

We will make the mouse-human PAX3-FKHR cDNA construct containing the first ATG available upon request. The complete annotated sequence has been submitted to GenBank under accession no. AF178854.