C/EBPbeta suppression by interruption of CUGBP1 resulting from a complex rearrangement of MLL.

Translocations involving the mixed-lineage leukemia gene (MLL) confer a poor prognosis in acute leukemias. In t(1;11)(q21;q23), MLL is fused reciprocally with AF1q. Here we describe a t(1;11)(q21;q23) with a secondary event involving insertion of the telomeric portion of MLL into the p arm of chromosome 11 (11p11). We show that this latter event interrupts the CUG triplet repeat binding protein-1 (CUGBP1) gene, a translational enhancer of C/EBPbeta. We then showed that these cells have reduced expression of CUGBP1 and C/EBPbeta when compared to other AML blasts. This is the first report to describe insertional disruption of the CUGBP1 gene and to suggest a role for the CUGBP1-C/EBPbeta pathway in leukemogenesis.