The protein FEZ1 (Fasciculation and Elongation protein Zeta-1) is an orthologue of C. elegans UNC-76, necessary for the formation and normal growth axon in this worm. Moreover, over-expression of FEZ1 induces a post-entry block of retroviruses in cultured cells. We employed the yeast two-hybrid system in order to identify proteins interacting with FEZ1 and thereby get clues on its cellular functional context. We identified the human proteins BAF60a (BRG1 Associated Factor a), SAP30L (Sin3A Associated Protein 30 Like) and SMC3 (Structural Maintenance of Chromosome 3), and FEZ1 itself among a total of 16 interacting proteins. BAF60a is related to the processes of the chromatin-remodeling activity. SAP30L is homologous to the SAP30, which associates with the transcription repression complex Sin3. A series of functions have been attributed to the protein SMC3 in eukaryotic cells, and its over-expression can induce tumoral cell growth. The cDNA fragments from the yeast two-hybrid prey vectors were cloned in bacterial expression vectors. The expressed proteins were used to confirm the interaction with FEZ1 in in vitro pull-down assay. For a more detailed structural and functional analysis the full lenght cDNAs encoding the interacting proteins were PCR-amplified, cloned and sub-cloned in both bacterial (BAF60a, SAP30L) or baculo virus (SMC3) systems. GST-SAP30L expressed as a soluble protein. It was purified and analyzed by circular dichroism spectroscopy and submitted to crystallization trials. The expression and purification of the other two proteins is still being optimized. The availability of pure recombinant proteins will allow a series of functional and structural studies in vitro. Furthermore, the proteins will be utilized in co-crystallization trials with FEZ1 and analytical gel-filtration studies for the characterization of the protein-complexes.