Positive and Negative Regulation of Granulocyte-Macrophage Colony-Stimulating Factor Promoter Activity by AML1-Related Transcription Factor, PEBP2

Abstract

The granulocyte-macrophage colony-stimulating factor (GM-CSF) gene promoter contains a consensus sequence for the polyomavirus enhancer binding-protein 2 (PEBP2) transcription factor, which consists of α and β subunits. There are at least two genes, αA and αB, encoding the α subunit. αB is the mouse homologue of human AML1 gene detected at the breakpoints of t(8;21) and t(3;21) myeloid leukemias. We examined αA1 (an αA-gene product) and αB1 and αB2 (two αB-encoded isomers) for their effects on the GM-CSF promoter. PEBP2αA1, αB1, and αB2 proteins bound the PEBP2 site within the mouse GM-CSF promoter. PEBP2αA1 and αB1 enhanced the expression of the GM-CSF promoter-driven reporter plasmid in unstimulated and 12-O-tetradecanoylphorbol 13 - acetate / phytohemagglutinin - stimulated human Jurkat T cells. In contrast, the promoter activity was suppressed by αB2. Coexpression of αB1 and αB2 showed that the promoter activity could be determined by the αB1/ αB2 ratio. Jurkat cell extract contained PEBP2 site-binding protein(s) that cross-reacted with antimouse αA1 antibodies. Northern blot analysis indicated the expression of human PEBP2αA, αB (AML1), and βgenes in Jurkat cells. Although further studies are required to determine the precise role of PEBP2 in the GM-CSF promoter activity, the present findings suggested the importance of the relative ratio of different PEBP2 isoforms in regulating the levels of the promoter activity. © 1995 by The American Society of Hematology.