NACA (Nascent-Polypeptide-Associated Complex α Subunit) Against Apoptosis in B Lymphoma Cell is Independent of β Subunit (NACB)

 We found depletion of NACA in two kinds of B lymphoma cell lines, Raji and Kapas, were able to induce apoptosis in this study. We also explored whether depletion of Z² subunit had the same effect, and we were interested in which domain of NACA was potentially responsible to this anti-apoptosis function. Lentivirus-based shRNA was used to deplete endogenous NACA or NACB. Those cells viabilities were measured by Alamar-blueTM assay. Cell apoptosis was identified by molecular markers caspase9 and PARP, as well as cellular markers Annexin V and propidium iodide (PI) staining. NACA mutants were constructed by PCR site-directed mutagenesis and delivered into cells by Lentivirus. Immunofluoresce was used to investigate cellular distribution in 293FT cells. Our results demonstrated that the depletion of NACA, but not NACB, was able to induce apoptosis. Deletion of middle or C-term rather than N-term induced obvious apoptosis. The middle part of NACA was response to bind NACB and form a complex. Without middle part, NACA redistributed into nuclei. We conclude NACA against apoptosis is independent of Z² subunit. C-term of NACA, which is identified as ubiquitin binding domain, and may take important role in anti-apoptosis function.