The WWOX gene is a recently cloned tumor suppressor gene that spans the FRA16D fragile region. Wwox protein contains two WW domains that are generally known to mediate protein-protein interaction. Here we show that Wwox physically interacts via its first WW domain with the p53 homolog, p73. The tyrosine kinase, Src, phosphorylates Wwox at tyrosine 33 in the first WW domain and enhances its binding to p73. Our results further demonstrate that Wwox expression triggers redistribution of nuclear p73 to the cytoplasm and, hence, suppresses its transcriptional activity. In addition, we show that cytoplasmic p73 contributes to the proapoptotic activity of Wwox. Our findings reveal a functional cross-talk between p73 and Wwox tumor suppressor protein.

The immediate early gene NUR77 (also called NGFI-B) is required for T cell antigen receptor-mediated cell death and is induced to very high levels in immature thymocytes and T cell hybridomas undergoing apoptosis. The Akt (PKB) kinase is a key player in transduction of anti-apoptotic and proliferative signals in T cells. Because Nur77 has a putative Akt phosphorylation site at Ser-350, and phosphorylation of this residue is critical for the transactivation activity of Nur77, we investigated whether Akt regulates Nur77. Coimmunoprecipitation experiments showed the detection of Nur77 in Akt immune complexes, suggesting that Nur77 and Akt physically interact. We further show that Akt specifically phosphorylates Ser-350 of the Nur77 protein within its DNA-binding domain in vitro and in vivo in 293 and NIH 3T3 cells. Because phosphorylation of Ser-350 of Nur77 is critical for its function as a transcription factor, we examined the effect of Akt on this function. By using luciferase assay experiments, we showed that phosphorylation of Nur77 by Akt decreased the transcriptional activity of Nur77 by 50 -85%. Thus, we show that Akt interacts with Nur77 and inactivates Nur77 by phosphorylation at Ser-350 in a phosphatidylinositol 3-kinase-dependent manner, connecting the phosphatidylinositol 3-kinase-dependent Akt pathway and a nuclear receptor pathway.

The T-cell receptor (TCR) a/6 chain locus on chromosome 14q11 is nonrandomly involved in translocations and inversions in human T-cell neoplasms. We have analyzed three acute T-lymphoblastic leukemia samples carrying a t(10;14)(q24;qll) chromosome translocation by means of somatic cell hybrids and molecular cloning. In all cases studied the translocation splits the TCR 6 chain locus. Somatic cell hybrids containing the human 10q+ chromosome resulting from the translocation retain the human terminal deoxynucleotidyltransferase gene mapped at 10q23-q24 and the diversity and joining, D82-Jr1, regions of the TCR 6 chain, but not the Va region (variable region of the TCR a chain), demonstrating that the split occurred within the Vr-Dg2 region. Molecular cloning of the breakpoint junctions revealed that the TCR 6 chain sequences involved are made from the D82 segment. The chromosome breakpoints are clustered within a region of -263 base pairs of chromosome 10. The results suggest that the translocation of the TCR 6 chain locus to a locus on 10q, which we have designated TCL3, results in deregulation of this putative oncogene, leading to acute T-cell leukemia.Chromosomal abnormalities, translocations, inversions, and deletions are nonrandomly associated with certain types of human leukemias and lymphomas (1). In T-cell tumors, many such abnormalities involve the T-cell receptor (TCR) a chain locus (TCRa) at chromosome band 14q11 (2)(3)(4)(5). The TCR 8 chain locus (TCR8) was identified between the 5' portion of the a chain joining segments and the TCRa variable region (Va) segments (6, 7). By means of somatic cell hybrids and molecular cloning of the entire 8 locus (3,8), this laboratory (2) and others (8, 9) were able to demonstrate the direct