Association of MTG8 (ETO/CDR), a leukemia-related protein, with serine/threonine protein kinases and heat shock protein HSP90 in human hematopoietic cell lines

A proto-oncogene, MTG8 (ETO/CDR), is disrupted in the t(8;21) translocation associated with acute myeloid leukemia, and the gene product, MTG8, is a p hosphoprotein capable of tell transformation in concert with v-H-ras, To ob tain insight into functional regulation of MTG8 by phosphorylation, we stud ied protein kinases that interact with, and phosphorylate, MTG8 in vitro. R ecombinant MTG8 protein was first found to be associated with tno serine/th reonine protein kinases in cell extracts from both HEL cells and a leukemic cell line carrying t(8;21), A cytoplasmic protein kinase of 61 kDa (MTG8N- kinase) phosphorylated the amino-terminal of MTG8, and another of 52 kDa (M TG8C-kinase) phosphorylated the carboxyl-terminal domain. In addition, we d emonstrated that heat shock protein 90 (HSP90) specifically binds to the am ino-terminal domain of MTG8 in vitro and in vivo. Thus, our results shed ne w light on post-translational regulation of MTG8, perturbation of which, in AML1-MTG8 protein, probably contributes to leukemogenesis.