title: Function of leukemogenic mixed lineage leukemia 1 (MLL) fusion proteins through distinct partner protein complexes.
abstract: A number of acute leukemias arise from fusion of the mixed lineage leukemia 1 protein (MLL) N terminus to a variety of fusion partners that have been reported to reside in one or more poorly defined complexes linked to transcription elongation through interactions with the histone H3-K79 methyltransferase DOT1 and positive transcription elongation factor b (P-TEFb). Here we first identify natural complexes (purified through fusion partners AF9, AF4, and ELL) with overlapping components, different elongation activities, and different cofactor associations that suggest dynamic interactions. Then, through reconstitution of defined, functionally active minimal complexes, we identify stable subcomplexes that, through newly defined protein-protein interactions, form distinct higher order complexes. These definitive analyses show, for example, that (i) through direct interactions with AF9 and cyclinT1, family members AF4 and AFF4 independently mediate association of P-TEFb with AF9, (ii) P-TEFb, through direct interactions, provides the link for association of ELL and ELL-associated factors 1 and 2 (EAF1 and EAF2) with AF4, and (iii) in the absence of other factors, DOT1 forms a stable complex with AF9 and does not interact with AF9•AF4•P-TEFb complexes. Finally, we show the importance of defined higher order complex formation in MLL-AF9-mediated transcriptional up-regulation and cell immortalization potential in vivo. Thus, our study provides direct mechanistic insight into the role of fusion partners in MLL fusion-mediated leukemogenesis.
authors: Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY 10065, USA.
authors: Debabrata
authors: D
authors: Biswas
authors: Thomas A
authors: TA
authors: Milne
authors: Venkatesha
authors: V
authors: Basrur
authors: Jaehoon
authors: J
authors: Kim
authors: Kojo S J
authors: KS
authors: Elenitoba-Johnson
authors: C David
authors: CD
authors: Allis
authors: Robert G
authors: RG
authors: Roeder
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D011495:Histone-Lysine N-Methyltransferase; D006657:Histones / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007938:Leukemia / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism*; D042925:Positive Transcriptional Elongation Factor B / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D018411:Spodoptera
chemical_list: C489900:Aff1 protein, mouse; D004268:DNA-Binding Proteins; D006657:Histones; D018398:Homeodomain Proteins; C489902:Mllt3 protein, mouse; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion; C097899:homeobox protein HOXA9; D051788:Myeloid-Lymphoid Leukemia Protein; C481527:Dot1l protein, mouse; D008780:Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D042925:Positive Transcriptional Elongation Factor B