PAK-2p34 is ubiquitinated prior to degradation (Jakobi et al., 2003). Here, ubiquitination of PAK-2p34 is described as occurring in the cytosol. However, to date it is not known whether this occurs in the nucleus or in the cytoplasm. Evidence for this reaction comes from experiments using both human and rabbit proteins. The polyubiquitin synthesized in the reaction is inferred to contain lysine-48 (K48) linkages because the modified protein is targeted to the proteasome (Komander 2009).