This entry includes animal NOSIP (nitric oxide synthase-interacting protein) and plant CSU1. They are ubiquitin E3 ligases [, ]. Human NOSIP negatively regulates nitric oxide production by inducing NOS1 and NOS3 translocation to actin cytoskeleton and inhibiting their enzymatic activity [, , ].Arabidopsis CSU1 plays a important role in maintaining COP1 homeostasis by targeting COP1 for ubiquitination and degradation in dark-grown seedlings [].