Negative regulation of granulocytic differentiation in the myeloid precursor cell line 32Dcl3 by ear-2, a mammalian homolog of Drosophila seven-up, and a chimeric leukemogenic gene, AML1/ETO(MTG8)

Department of Viral Oncology, Institute for Virus Research, Kyoto University, Shogoin, Sakyo-ku, Kyoto 606, Japan

Communicated by Wolfgang K. Joklik, Duke University Medical Center, Durham, NC (received for review November 4, 1997)

Abstract

The polyomavirus enhancer binding protein 2αB (AML1/PEBP2αB/Cbfa2) plays a pivotal role in granulocyte colony-stimulating factor (G-CSF)-mediated differentiation of a myeloid progenitor cell line, 32Dc13. In this article, we report the identification of a PEBP2αB interacting protein, Ear-2, an orphan member of the nuclear hormone receptor superfamily that directly binds to and can inhibit the function of PEBP2αB. Ear-2 is expressed in proliferating 32Dc13 cells in presence of interleukin 3 but is down-regulated during differentiation induced by G-CSF. Interestingly, AML1/ETO(MTG8), a leukemogenic chimeric protein can block the differentiation of 32Dc13 cells, which is accompanied by the sustained expression of ear-2. Overexpression of Ear-2 can prevent G-CSF-induced differentiation, strongly suggesting that ear-2 is a key negative regulator of granulocytic differentiation. Our results indicate that a dynamic balance existing between PEBP2αB and Ear-2 appears to determine the choice between growth or differentiation for myeloid cells.

Footnotes

↵ * Present address: College of Medicine, Chungbuk National University. Chungju 360–763, Korea.
↵ † To whom reprint requests should be addressed. e-mail: yito{at}virus.kyoto-u.ac.jp.
ABBREVIATIONS:

PEBP2αB,

polyomavirus enhancer binding protein 2 αB;

G-CSF,

granulocyte colony-stimulating factor;

IL-3,

interleukin 3;

GST,

glutathione S-transferase;

G-CSF-R,

G-CSF receptor