Amplification of a DEAD box gene (DDX1) with the MYCN gene in neuroblastomas as a result of cosegregation of sequences flanking the MYCN locus
✍ Scribed by Tohru Noguchi; Kiyotaka Akiyama; Masahiro Yokoyama; Naotoshi Kanda; Tadashi Matsunaga; Yoshisuke Nishi
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 362 KB
- Volume
- 15
- Category
- Article
- ISSN
- 1045-2257
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✦ Synopsis
A DEAD box gene (DDXI) characterized by a motif with a putative RNA helicase was found at elevated levels, with multiple copies, in a neuroblastorna and in some retinoblastoma cell lines in which the MYCN gene was amplified. The present study was aimed at determining whether amplification o f the DDXl gene is critical for human neuroblastomas exhibiting MYCN gene amplification. Extended DNA panels of tumors and cell lines revealed amplification of the DDXl gene in approximately half of the specimens exhibiting MYCN gene amplification, which is in good agreement with a finding reported recently. Because its profile was similar t o that of the cDNA marker G2 I and another flanking DNA marker, clone 8, both o f which localize outside the core of the amplicon of the MYCN gene, we noted that we could localize the DDXl gene in relation t o the MYCN gene. Utilizing pulsed-field gel electrophoresis according t o a method based on the combinatorial alignment of multiple single digests and a 5.5-megabase map surrounding the MYCN locus, we mapped the DDXl gene within a 100 kb region about 400 kb upstream from the MYCN gene, where G2I is localized. Further hybridization experiments with both genes, complete sequencing of G2 I, and its comparison with that of the DDXl gene eventually confirmed that the DDXl gene is identical to G2 I . G2 I is a cDNA clone isolated by differential screening of a library from a neuroblastoma cell line, IMR-32, but its function has not yet been identified. Coamplification of the DDXl gene with the MYCN gene is a consequence of the segregation of continuous DNA stretches spanning both loci during the amplification process.