ENL, the MLL fusion partner in t(11;19), binds to the c-Abl interactor protein 1 (ABI1) that is fused to MLL in t(10;11)+

Abstract

Translocations of the chromosomal locus 11q23 that disrupt the MLL gene (alternatively ALL-1 or HRX) are frequently found in children's leukemias. These events fuse the MLL amino terminus in frame with a variety of unrelated proteins. Up to date, 16 di erent fusion partners have been characterized and more are likely to exist. No general unifying property could yet be detected amongst these proteins. We show here that the frequent MLL fusion partner ENL at 19p13.1 interacts with the human homologue of the mouse Abl-Interactor 1 (ABI1) protein. ABI1 in turn, is fused to MLL in the t(10;11)(p11.2;q23) translocation. ABI1 was identi®ed as an ENL binding protein by a yeast two-hybrid screen. The interaction of ENL and ABI1 could be veri®ed in vitro by far-Western blot assays and GST-pulldown studies as well as in vivo by co-immunoprecipitation experiments. A structure-function analysis identi®ed an internal region of ENL and a composite motif of ABI1 including an SH3 domain as mutual binding partners. These data introduce novel aspects that might contribute to the understanding of the process of leukemogenesis by MLL fusion proteins.

The heterogeneity of pediatric MLL-rearranged acute myeloid leukemia

“…Indeed when the ABI1 protein, a fusion partner of MLL, is imported into the nucleus, it interacts with MLLT1. 61 In gene expression profiling (GEP) studies, MLL-rearranged cases clustered together as one group in AML as well as in ALL. 13,[62][63][64] However, our laboratory showed that within MLL-rearranged infant ALL each type of MLL translocation is associated with a translocation-specific gene expression signature.…”

The eleven-nineteen-leukemia protein ENL connects nuclear MLL fusion partners with chromatin

“…Structure-function analysis of MLL-ENL has shown that the ENL C-terminus is necessary and sufficient for transformation and provides a proteinprotein interaction surface with transactivator potential (Slany et al, 1998). The ENL C-terminus interacts with another MLL fusion partner, ABI-1, once this normally cytoplasmatic protein has been imported into the nucleus by the fusion with MLL (Garcia-Cuellar et al, 2000). Moreover, the same domain of ENL also recruits the protein PC3 (polycomb3, also termed CBX8 for chromobox protein 8), a factor involved in chromatin remodeling .…”

“…(b) Schematic representation of a set of GAL4 DNA-BD ENL mutants established during a previous study (Garcia-Cuellar et al, 2000). All mutant clones had been tested before for correct expression and potential autonomous transactivation capability (Garcia-Cuellar et al, 2000). An immunoblot controlling for the presence of a full-length GAL4-ENL fusion in yeast extracts is shown in the inset.…”

“…Upon retransformation into yeast all initially isolated library plasmids again supported growth on selective dropout media (Figure 1a). In a test with an existing bait-series of ENL mutants that had been established during earlier studies (Garcia-Cuellar et al, 2000, the library encoded GAL4-AF4, GAL4-AF5q31, and GAL4-AF10 all interacted with a C-terminal portion of ENL (Figure 1b). In contrast to PC3, the nuclear MLL fusion partners also bound to a mutant version of the ENL C-terminus lacking the last 15 amino acids.…”

“…Accession numbers for insert sequences are: ENL (NM005934), AF4 (NM005935), AF5q31 (NM014423), AF10 (NM0 04641). (b) Schematic representation of a set of GAL4 DNA-BD ENL mutants established during a previous study (Garcia-Cuellar et al, 2000). All mutant clones had been tested before for correct expression and potential autonomous transactivation capability (Garcia-Cuellar et al, 2000).…”