Nuclear proteins get around

Protein trafficking between the cytoplasm and the nucleus has been studied extensively; but how do proteins move from one site to another within the nucleus? On page 615, Leung and Lamond focus on the intranuclear trafficking of the RNA-binding protein NHPX, and describe an elegant series of experiments that demonstrates the existence of multiple intranuclear accumulation pathways. The study provides definitive evidence of protein sorting within the nucleus.Although previous studies have suggested that proteins might follow directed paths between intranuclear bodies, the new work provides a detailed analysis of this phenomenon. NHPX localizes primarily to nucleoli, but is capable of binding to both small nucleolar RNAs (snoRNAs) and the spliceosomal U4 small nuclear RNA (snRNA). The authors followed fluorescent fusion proteins to determine that newly...