PEBP2/CBF, the Murine Homolog of the Human Myeloid AML1 and PEBP2β/CBFβ Proto-oncoproteins, Regulates the Murine Myeloperoxidase and Neutrophil Elastase Genes in Immature Myeloid Cells

Abstract

The myeloperoxidase (MPO) and neutrophil elastase genes are expressed specifically in immature myeloid cells. The integrity of a polyomavirus enhancer core sequence, 5′-AACCACA-3′, is critical to the activity of the murine MPO proximal enhancer. This element binds two species, myeloid nuclear factors 1α and 1β (MyNFlot and -β), present in 32D cl3 myeloid cell nuclear extracts. The levels of the MyNFls increase during early 32D cl3 cell granulocytic differentiation. Both MyNFlα and β supershift with an antiserum raised by using a peptide derived from the N terminus of polyomavirus enhancer-binding protein 2/core-binding factor (PEBP2/CBF) α subunit. The specific peptide inhibits these supershifts. In vitro-translated PEBP2/CBF DNA-binding domain binds the murine MPO PEBP2/CBF site. An alternate PEBP2/CBF consensus site, 5′-GACCGCA-3′, but not a simian virus 40 enhancer core sequence, 5′-TTCCACA-3′, binds the MyNFls in vitro and activates a minimal murine MPO-thymidine kinase promoter in vivo. The murine neutrophil elastase gene 100-bp 5′-flanking sequences contain several functional elements, including potential binding sites for PU.1, C/EBP, c-Myβ, and PEBP2/CBF. The functional element 5′-GGCCACA-3′ located at positions —66 to 72 differs from the PEBP2/CBF consensus (5′-PuACCPuCA-3′) only by an A-to-G transition at position 2. This DNA element binds MyNFlα and β weakly. The N terminis of two PEBP2/CBF α subunit family members, PEBP2αA and PEBP2αB (murine AML1), are nearly identical, and 32D cl3 cells contain both corresponding mRNAs. Since t(8;21), t(3;21), and inv(16), associated with myeloid leukemias, disrupt subunits of PEBP2/ CBF, we speculate that the resulting oncoproteins, AML1-ETO, AML1-EAP, AML1-Evil, and CBFβ-MYH11, inhibit early myeloid differentiation.