The HOX-11 (TCL-3) homeobox proto-oncogene encodes a nuclear protein that undergoes cell cycle-dependent regulation

Molecular analysis of the t(10;14) chromosomal translocation found in pediatric patients with T-cell acute lymphoblastic leukemia has led to the identification of the HOX-11 (TCL-3) protooncogene. The HOX-11 cDNA contains an open reading frame encoding a homeoprotein with features of DNA-binding. The majority of the t(10;14) chromosomal translocation breakpoints have been mapped to the 5' end of the HOX-11 gene, supporting the notion that deregulation of the HOX-11 gene by the t(10;14) chromosomal translocation contributed importantly to leukemia formation. To further define the role of the HOX-11 homeoprotein, we have prepared rabbit antiserum against a trpE-HOX-11 fusion protein. The purified anti-HOX-11 IgG immuno-precipitated a protein with apparent relative molecular mass of 40 kD. Biochemical fractionation demonstrated that the protein is localized in the nucleus. Furthermore, the HOX-11 RNA and protein appeared to be modulated during the cell cycle, with the highest level of expression at G1/S phase boundary. Taken together, these data suggest that the HOX-11 gene product may function as a transcription factor for G1 progression in the cell cycle.