The influence of phosphorylation of prothymosin α on its nuclear import and antiapoptotic activity

Phosphorylation of prothymosin α (ProTα) appears not to affect its influence on chromatin remodelling. To determine whether it affects nuclear import or cytosolic antiapoptotic activity, cells were transfected with vectors generating tagged recombinant ProTα (rProTα), either wild-type (rProTα-wt), which is partially phosphorylated posttranslation or the nonphosphorylatable rProTα-T7A. Immunofluorescence microscopy showed the predominant location of native ProTα, rProTα-wt, and rProTα-T7A in the nucleus. The activity of caspases 9 and 3 following apoptosis induction treatment (staurosporine) indicated reduction of apoptosis by rProTα-wt but not by rProTα-T7A. It is concluded that phosphorylation of ProTα is required for its antiapoptotic activity, but it does not affect its nuclear import.