Two candidate downstream target genes for E2A-HLF.
The E2A-HLF fusion gene, formed by the t(17;19)(q22;p13) chromosomal translocation, is thought to drive the leukemic transformation of early B-cell precursors by repressing an evolutionarily conserved apoptotic pathway. To test this hypothesis, we sought to identify downstream targets of E2A-HLF in t(17;19)+ pro-B leukemia cells (UOC-B1) that had been transfected with a zinc-inducible vector encoding a dominant-negative suppressor (E2A-HLF[dn]) of the oncoprotein. Representational difference analysis of mRNAs from E2A-HLF(dn)+ UOC-B1 cells grown with (E2A-HLF inactive) or without (E2A-HLF active) the addition of zinc yielded several differentially expressed cDNA fragments that were individually subcloned. Two of the clones, designated F-5 and G-4, hybridized with mRNAs that were upregulated by E2A-HLF. Levels of both transcripts declined sharply within 8 to 12 hours after suppression of E2A-HLF DNA-binding activity, becoming undetectable after 96 hours. The F-5 cDNA was identified as a portion of ANNEXIN VIII, whose product was expressed in promyelocytic leukemia cells and UOC-B1 cells, but not in other leukemic cell lines. A novel full-length cDNA cloned with the G-4 fragment encoded a protein that we have named SRPUL (sushi-repeat protein upregulated in leukemia). It is normally expressed in heart, ovary, and placenta, but could not be detected in leukemic cell lines other than UOC-B1. Neither protein prevented apoptosis in interleukin-3-dependent murine pro-B cells, suggesting that they have paraneoplastic roles in leukemias that express E2A-HLF, perhaps in the disseminated intravascular coagulopathy and hypercalcemia that characterize these cases.[1]References
- Two candidate downstream target genes for E2A-HLF. Kurosawa, H., Goi, K., Inukai, T., Inaba, T., Chang, K.S., Shinjyo, T., Rakestraw, K.M., Naeve, C.W., Look, A.T. Blood (1999) [Pubmed]
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