LAF-4 encodes a lymphoid nuclear protein with transactivation potential that is homologous to AF-4, the gene fused to MLL in t(4;11) leukemias

A novel human gene, LAF-4, was isolated from a subtracted cDNA library that showed strong sequence similarity to AF-4, a gene that is translocated in t(4;11)(q21;q23) acute lymphoblastic leukemias (ALLs). In t(4;ll) ALL, the AF-4 gene at 4q21 is translocated into the MLL locus at 11q23, resulting in the expression of an MLL/AF4 fusion protein that is the presumptive oncoprotein. AF-4 and LAF-4 are homologous throughout their coding regions, yet neither protein is related to previously cloned genes. Human LAF-4 readily hybridized with genes in mouse and chicken, thus showing that this gene family has been highly conserved during vertebrate evolution. In mouse tissues, LAF-4 mRNA was found t o be present at highest levels in lymphoid tis-sues, present at lower levels in brain and lung, and absent from other tissues. In human and mouse lymphoid cell lines