Overexpression of the BRE (brain and reproductive organ-expressed) gene defines a distinct pediatric and adult acute myeloid leukemia (AML) subgroup. Here we identify a promoter enriched for active chromatin marks in BRE intron 4 causing strong biallelic expression of a previously unknown C-terminal BRE transcript. This transcript starts with BRE intron 4 sequences spliced to exon 5 and downstream sequences, and if translated might code for an N terminally truncated BRE protein. Remarkably, the new BRE transcript was highly expressed in over 50% of 11q23/KMT2A (lysine methyl transferase 2A)-rearranged and t(8;16)/KAT6A-CREBBP cases, while it was virtually absent from other AML subsets and normal tissues. In gene reporter assays, the leukemia-specific fusion protein KMT2A-MLLT3 transactivated the intragenic BRE promoter. Further epigenome analyses revealed 97 additional intragenic promoter marks frequently bound by KMT2A in AML with C-terminal BRE expression. The corresponding genes may be part of a context-dependent KMT2A-MLLT3-driven oncogenic program, because they were higher expressed in this AML subtype compared with other groups. C-terminal BRE might be an important contributor to this program because in a case with relapsed AML, we observed an ins(11;2) fusing CHORDC1 to BRE at the region where intragenic transcription starts in KMT2A-rearranged and KAT6A-CREBBP AML.

Additional Metadata
Persistent URL dx.doi.org/10.1038/leu.2017.280, hdl.handle.net/1765/105084
Journal Leukemia
Citation
Marneth, A.E. (A. E.), Prange, K.H.M. (K. H.M.), Al Hinai, A.S.A, Bergevoet, S.M. (S. M.), Tesi, N. (N.), Janssen-Megens, E.M. (E. M.), … Martens, J.H.A. (2018). C-terminal BRE overexpression in 11q23-rearranged and t(8;16) acute myeloid leukemia is caused by intragenic transcription initiation. Leukemia, 32(3), 828–836. doi:10.1038/leu.2017.280