The chromosomal translocation t(X;14)(q28;q11) in T-cell pro-lymphocytic leukaemia breaks within one gene and activates another.

Chromosomal translocation t(X;14)(q28;q11) has been observed in patients with pro-lymphocytic T-cell leukaemia (T-PLL). In two cases of T-PLL, one of which was associated with Ataxia telangiectasia (AT), the chromosomal break occurred in two different introns of a gene c6.1A, located at the Xq28 locus. Fusion transcripts, consisting of 5' sequences of c6.1A and the TCRα constant (C) region, were expressed at high levels in the leukaemic cells from both patients, but in only one case did this fusion generate an in-frame c6.1A-Cα mRNA. However, the breaks within c6.1A seem to affect another gene, c6.1B, which is transcribed from the same CpG rich island as c6.1A but in the opposite transcriptional orientiation