The constitutive 3p14.2 fragile site is the most highly inducible fragile site in the human genome. This locus may predispose chromosome 3 to specific losses due to deletions and translocations that have been associated with several malignancies, including hereditary renal cell carcinoma. Using aphidicolin concentrations of 0.4 and 4.0 μM, we have generated and isolated 23 and 22 respective somatic cell hybrids that contain chromosome 3 short-arm breaks. The breakpoints in these hybrids have been localized with numerous chromosome 3 markers. We have observed that at the low aphidicolin dose, chromosome-3 breaks cluster within the 3p14.2 region, whereas at the high aphidicolin dose, two new loci, one within 3p14.1 and the other near the centromere, become predominantly affected. Our studies have failed to differentiate any of the 3p14.2 breakpoints from each other or from the t(3;8)(p14.2;q24.13) familial renal cell carcinoma translocation breakpoint, suggesting that the fragile site may have played a role in the generation of this balanced translocation. The resulting somatic cell hybrids generated from this work have refined the marker localizations within 3p13-p21.1 and should facilitate the physical characterization of this interesting region.
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