The non-random chromosomal translocations t(10;11)(p13;q23) and t(10;11)(p13;q14–21) result in leukemogenic fusion proteins comprising the coiled coil domain of the transcription factor AF10 and the proteins MLL or CALM, respectively, and subsequently cause certain types of acute leukemia. The AF10 coiled-coil domain, which is crucial for the leukemogenic effect, has been shown to interact with GAS41, a protein previously identified as the product of an amplified gene in glioblastoma. Using sequential synthetic peptides, we mapped the potential AF10/GAS41 interaction site, which was subsequently be used as scaffold for a library targeting the AF10 coiled-coil domain. Using phage display, we selected a peptide that binds the AF10 coiled-coil domain with higher affinity than the respective coiled-coil region of wild-type GAS41, as demonstrated by phage ELISA, CD, and PCAs. Furthermore, we were able to successfully deploy the inhibitory peptide in a mammalian cell line to lower the expression of Hoxa genes that have been described to be overexpressed in these leukemias. This work dissects molecular determinants mediating AF10-directed interactions in leukemic fusions comprising the N-terminal parts of the proteins MLL or CALM and the C-terminal coiled-coil domain of AF10. Furthermore, it outlines the first steps in recognizing and blocking the leukemia-associated AF10 interaction in histiocytic lymphoma cells and therefore, may have significant implications in future diagnostics and therapeutics. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.
This article describes the design and selection of an interfering peptide that binds and blocks the AF10 coiled-coil domain of the leukemia-associated CALM–AF10 fusion protein. The anti-AF10 peptide binds tighter than AF10 wild-type interaction partners and is able to lower hDOT1L-mediated overexpression of Hoxa genes that have been linked to leukemogenesis.