Regulation of mir-196b by MLL and its overexpression by MLL fusions contributes to immortalization.
Chromosomal translocations involving the Mixed Lineage Leukemia (MLL) gene produce chimeric proteins that cause abnormal expression of a subset of HOX genes and leukemia development. Here, we show that MLL normally regulates expression of mir-196b, a hematopoietic microRNA located within the HoxA cluster, in a pattern similar to that of the surrounding 5' Hox genes, Hoxa9 and Hoxa10, during embryonic stem (ES) cell differentiation. Within the hematopoietic lineage, mir-196b is most abundant in short-term hematopoietic stem cells and is down-regulated in more differentiated hematopoietic cells. Leukemogenic MLL fusion proteins cause overexpression of mir-196b, while treatment of MLL-AF9 transformed bone marrow cells with mir-196-specific antagomir abrogates their replating potential in methylcellulose. This demonstrates that mir-196b function is necessary for MLL fusion-mediated immortalization. Furthermore, overexpression of mir-196b was found specifically in patients with MLL associated leukemias as determined from analysis of 55 primary leukemia samples. Overexpression of mir-196b in bone marrow progenitor cells leads to increased proliferative capacity and survival, as well as a partial block in differentiation. Our results suggest a mechanism whereby increased expression of mir-196b by MLL fusion proteins significantly contributes to leukemia development.
Popovic
Relja
R
Molecular Biology Program, Loyola University Medical Center, Maywood, IL, USA.
Riesbeck
Laurie E
LE
Velu
Chinavenmeni S
CS
Chaubey
Aditya
A
Zhang
Jiwang
J
Achille
Nicholas J
NJ
Erfurth
Frank E
FE
Eaton
Katherine
K
Lu
Jun
J
Grimes
H Leighton
HL
Chen
Jianjun
J
Rowley
Janet D
JD
Zeleznik-Le
Nancy J
NJ
D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation / Q000235:genetics; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000473:pathology; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000378:metabolism / Q000473:pathology / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology; D011495:Histone-Lysine N-Methyltransferase; D007938:Leukemia / Q000209:etiology / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D051788:Myeloid-Lymphoid Leukemia Protein / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012689:Sequence Homology, Nucleic Acid; D015854:Up-Regulation / Q000502:physiology
C542543:MIRN196 microRNA, human; D035683:MicroRNAs; D011993:Recombinant Fusion Proteins; D051788:Myeloid-Lymphoid Leukemia Protein; D011495:Histone-Lysine N-Methyltransferase; C497423:Kmt2a protein, mouse