have confirmed that CBFb binds to at least the first 140 amino acids of HIV-1 Vif. Thus, the known proteinbinding domains in Vif, including the EloB/C binding BC-box, the cullin box containing the PPLP motif, are not essential for the Vif-CBFb interaction. Vif forms homo-oligomers, and the PPLP motif has been suggested to be required for oligomerization. Since Vif140 still forms oligomers with CBFb140, CBFb182, and CBFb187, our results suggest that regions in Vif in addition to PPLP may also participate in Vif oligomerization. This conclusion is consistent with the recent finding that the PPLP motif is not sufficient for Vif multimerization. Biophysical and structural information for Vif has been limited as a result of its insolubility and strong tendency to oligomerize into high molecular weight aggregates. Of note, previous biochemical studies have employed full-length Vif protein obtained by the denaturing/refolding method or have used truncated tagged protein. Interestingly, when CBFb and EloB/C were present, even untagged full-length Vif could be purified as a stable and soluble complex. Association of Vif with CBFb alone, and especially in combination with EloB/C, greatly increases the solubility of fulllength Vif. We have shown that a stable complex containing VifCBFb140-EloB/C can be purified in large quantities. This complex appeared to contain one subunit of each protein and did not dissociate upon RNase treatment. More importantly, the Vif-CBFb140-EloB/C complexes we produced could interact with purified Cul5 and form stable Vif-CBFb140-EloB/C-Cul5 complexes. This successful purification of monomeric Vif-E3 ligase complexes in high purity will greatly facilitate biochemical studies, structural determination, and functional analyses in this field. Because CBFb is a unique regulator of Vif’s ability to hijack the cellular CRL5 E3 ligase, disrupting interactions within the VifCBFb140-EloB/C-Cul5 complex represents an exciting drug strategy for targeting HIV-1. Inhibitors that prevent complex formation would be potential candidates for HIV-1 suppression, and purification of these Vif complexes in homogeneous form would provide ” the basis for screens to identify and evaluate inhibitor candidates. Thus, our strategy for purifying Vif-Cul5- 7 Interaction between Vif, CBFb, E3 Ligase Complexes CBFb-EloB/C complexes may lead to useful screening approaches for identifying novel anti-HIV drug candidates. Antibody against Vif was obtained through the 11277518” AIDS Research and Reference Reagent Program, Division 
of AIDS, NIAID, National Institutes of Health. Malignant progression of cancer cells depends on intrinsic crosstalk between several factors, BCTC overexpression of various oncogenic molecules and loss of function of tumor suppressor genes. Therefore, understanding the mechanisms of various tumor suppressor genes in regulation of cancer progression and their possible role in cancer therapeutics is under intense investigation. Semaphorins have been originally known as a large family of evolutionary conserved axonal guidance molecules. The role of semaphorins in various physiological as well as pathophysiological processes including cell migration, regulation of immune response, angiogenesis and cancer have recently been studied. Among various semaphorins, selected members of semaphorin 3 family are involved in suppression of tumor progression and have been considered as potent tumor suppressors. Loss of expressions of Sema 3B and Sema 3F gene h
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