The (4;11)(q21;p15) Translocation Fuses the NUP98 andRAP1GDS1 Genes and Is Recurrent in T-Cell Acute Lymphocytic Leukemia

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Abstract
We determined the breakpoint genes of the translocation t(4;11)(q21;p15) that occurred in a case of adult T-cell acute lymphocytic leukemia (T-ALL). The chromosome 11 breakpoint was mapped to the region between D11S470 and D11S860. The nucleoporin 98 gene (NUP98), which is rearranged in several acute myeloid leukemia translocations, is located within this region. Analysis of somatic cell hybrids segregating the translocation chromosomes showed that the chromosome 11 breakpoint occurs withinNUP98. The fusion partner of NUP98 was identified as theRAP1GDS1 gene using 3′ RACE. RAP1GDS1 codes for smgGDS, a ubiquitously expressed guanine nucleotide exchange factor that stimulates the conversion of the inactive GDP-bound form of several ras family small GTPases to the active GTP-bound form. In theNUP98-RAP1GDS1 fusion transcript (abbreviated asNRG), 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 armadillo repeats. NRG fusion transcripts were detected in the leukemic cells of 2 other adult T-ALL patients. One of these patients had a variant translocation with a more 5′ breakpoint in NUP98. This is the first report of anNUP98 translocation in lymphocytic leukemia and the first time that RAP1GDS1 has been implicated in any human malignancy.