EBF1 and neoplasm: Putative EBF1 binding sites are present in the Cd244 promoter and upstream regulatory module (JH, unpublished data), and EBF1 negatively regulates Cd244 expression.14 We also examined Irf4 and Spi1 transcript levels as mice lacking expression of both Spi1 (encodes PU.1) and IRF4 in B cells spontaneously develop pre-B leukemia.24 However, although levels of Irf4 transcripts are significantly decreased in EB tumor cells, levels of Spi1 transcripts were not significantly altered (Supplementary Figure S5).