The Mdm2 oncoprotein is a well-known inhibitor of the p53 tumor suppressor, but it may also possess p53-independent activities. In search of such p53-independent activities, the yeast two-hybrid screen was employed to identify Mdm2-binding proteins. We report that in vitro and in transfected cells, Mdm2 can associate with Numb, a protein involved in the determination of cell fate. This association causes translocation of overexpressed Numb into the nucleus and leads to a reduction in overall cellular Numb levels. Through its interaction with Numb, Mdm2 may influence processes such as differentiation and survival. This could potentially contribute to the altered properties of tumor cells which overexpress Mdm2.

The mitochondrial outer membrane of eukaryotic cells contains voltage-dependent anion channels (VDAC) also termed porins. Three cDNAs from wheat (Triticum aestivum) were isolated and sequenced (Tavdac 1-3). They share 65% similarity of their amino acid sequences, and therefore they probably represent isoforms. The deduced amino acid sequence of one of the cDNAs was found to be identical to the purified VDAC protein from wheat mitochondria [8]. Secondary structure analysis of the deduced amino acid sequences of the three vdac cDNAs revealed a characteristic alpha helix at their N-terminal and beta-barrel cylinders characteristic of VDAC channels. The Tavdac cDNAs are differentially expressed in meristematic tissues. The transcript levels of Tavdac 1 in all wheat tissues is at least 2.5-fold higher than Tavdac 2 and Tavdac 3. Tavdac 2 has a low level of expression in all floral tissues whereas Tavdac 3 is highly expressed in anthers. This is the first report on differential expression of vdac genes in plants. The Tavdac genes have been mapped on the wheat genome. Tavdac 1 is located on the long arm of chromosome 5, Tavdac 2 on the long arm of chromosome 1 and Tavdac 3 on the long arm of chromosome 3. A phylogenetic reconstruction indicates that vdac genes underwent numerous duplication events throughout their evolution. All duplications occurred after the separation of plants from animals and fungi, and no orthologous genes are shared among phyla. Within plants, some of the vdac gene duplications probably occurred before the monocotydelon-dicotydelon split.

The p53 tumor suppressor gene is mutated in over 50% of human cancers, resulting in inactivation of the wild-type (wt) p53 protein. The most notable biochemical feature of p53 is its ability to act as a sequence-specific transcriptional activator. Through use of the suppression subtractive hybridization differential screening technique, we identified c-fos as a target for transcriptional stimulation by p53 in cells undergoing p53-mediated apoptosis. Overexpression of wt p53 induces c-fos mRNA and protein. Moreover, in vivo induction of c-fos in the thymus following whole-body exposure to ionizing radiation is p53 dependent. p53 responsiveness does not reside in the basal c-fos promoter. Rather, a distinct region within the c-fos gene first intron binds specifically to p53 and confers upon the c-fos promoter the ability to become transcriptionally activated by wt p53. Identification of c-fos as a specific target for transcriptional activation by p53 establishes a direct link between these two pivotal regulatory proteins and raises the possibility that c-fos contributes to some of the biological effects of p53.

CCL2 is a key CC chemokine that has been implicated in a variety of inflammatory autoimmune diseases and in tumor progression and it is therefore an important target for therapeutic intervention in these diseases. Soluble receptor-based therapy is a known approach for neutralizing the in vivo functions of soluble mediators. Owing to the complexity of seven-transmembrane G protein-coupled receptors, efforts to generate neutralizing soluble chemokine receptors have so far failed. We developed a strategy that is based on the generation of short recombinant proteins encoding different segments of a G protein-coupled receptor, and tested the ability of each of them to bind and neutralize its target chemokine. We show that a fusion protein comprised of as few as 20 aa of the third extracellular (E3) domain of the CCL2 receptor, stabilized by the IgG H chain Fc domain (E3-IgG or BL-2030), selectively binds CCL2 and CCL16 and effectively neutralizes their biological activities. More importantly, E3-IgG (BL-2030) could effectively suppress the in vivo biological activity of CCL2, attenuating ongoing experimental autoimmune encephalomyelitis, as well as the development of human prostate tumor in SCID mice.

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