The leukemogenic t(8;21) fusion protein AML1-ETO controls rRNA genes and associates with nucleolar-organizing regions at mitotic chromosomes.
RUNX1/AML1 is required for definitive hematopoiesis and is frequently targeted by chromosomal translocations in acute myeloid leukemia (AML). The t(8;21)-related AML1-ETO fusion protein blocks differentiation of myeloid progenitors. Here, we show by immunofluorescence microscopy that during interphase, endogenous AML1-ETO localizes to nuclear microenvironments distinct from those containing native RUNX1/AML1 protein. At mitosis, we clearly detect binding of AML1-ETO to nucleolar-organizing regions in AML-derived Kasumi-1 cells and binding of RUNX1/AML1 to the same regions in Jurkat cells. Both RUNX1/AML1 and AML1-ETO occupy ribosomal DNA repeats during interphase, as well as interact with the endogenous RNA Pol I transcription factor UBF1. Promoter cytosine methylation analysis indicates that RUNX1/AML1 binds to rDNA repeats that are more highly CpG methylated than those bound by AML1-ETO. Downregulation by RNA interference reveals that RUNX1/AML1 negatively regulates rDNA transcription, whereas AML1-ETO is a positive regulator in Kasumi-1 cells. Taken together, our findings identify a novel role for the leukemia-related AML1-ETO protein in epigenetic control of cell growth through upregulation of ribosomal gene transcription mediated by RNA Pol I, consistent with the hyper-proliferative phenotype of myeloid cells in AML patients.
Bakshi
Rachit
R
Department of Cell Biology and Cancer Center, University of Massachusetts Medical School, Worcester, MA 01655, USA.
Zaidi
Sayyed K
SK
Pande
Sandhya
S
Hassan
Mohammad Q
MQ
Young
Daniel W
DW
Montecino
Martin
M
Lian
Jane B
JB
van Wijnen
Andre J
AJ
Stein
Janet L
JL
Stein
Gary S
GS
D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000378:metabolism; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics*; D002898:Chromosomes, Human, Pair 8 / Q000235:genetics*; D050676:Core Binding Factor Alpha 2 Subunit / Q000235:genetics* / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D020459:Genes, rRNA / Q000235:genetics*; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000235:genetics*; D008938:Mitosis / Q000235:genetics*; D009697:Nucleolus Organizer Region / Q000378:metabolism*; D015514:Oncogene Proteins, Fusion / Q000235:genetics* / Q000378:metabolism; D000075142:RUNX1 Translocation Partner 1 Protein; D014178:Translocation, Genetic / Q000235:genetics
C107844:AML1-ETO fusion protein, human; D050676:Core Binding Factor Alpha 2 Subunit; D015514:Oncogene Proteins, Fusion; D000075142:RUNX1 Translocation Partner 1 Protein; C493728:RUNX1 protein, human