The (4;11)(q21;p15) translocation fuses the NUP98 and RAP1GDS1 genes and is recurrent in T-cell acute lymphocytic leukemia

We determined the breakpoint genes of the translocation t(4;11)(q21:p15) th at occurred in a case of adult T-cell acute lymphocytic leukemia (T-ALL), T he chromosome 11 breakpoint was mapped to the region between D11S470 and D1 1S860. The nucleoporin 98 gene (NUP98), which is rearranged in several acut e myeloid leukemia translocations, is located within this region. Analysis of somatic cell hybrids segregating the translocation chromosomes showed th at the chromosome 11 breakpoint occurs within NUP98. The fusion partner of NUP98 was identified as the RAP1GDS1 gene using 3' RACE. RAP1GDS1 codes for smgGDS, a ubiquitously expressed guanine nucleotide exchange factor that s timulates the conversion of the inactive GDP-bound form of several ras fami ly small GTPases to the active GTP-bound form. In the NUP98-RAP1GDS1 fusion transcript (abbreviated as NRG), the 5' end of the NUP98 gene is joined in frame to the coding region of the RAP1GDS1 gene. This joins the FG repeat- rich region of NUP98 to RAP1GDS1, which largely consists of tandem armadill o repeats, NRG fusion transcripts were detected in the leukemic cells of 2 other adult T-ALL patients. One of these patients had a variant translocati on with a more 5' breakpoint in NUP98, This is the first report of an NUP98 translocation in lymphocytic leukemia and the first time that RAP1GDS1 has been implicated in any human malignancy, (C) 1999 by The American Society of Hematology.