Genetic and biochemical methods for identifying protein interaction motifs that confer nuclear localization

许多蛋白质通过特定的定位信号精确定位到特定的亚细胞区室。蛋白质的核输入通常是通过核定位信号（NLSs）与可溶性细胞质受体蛋白相互作用介导的。典型NLSs包含一个短链的基本氨基酸（单链）或两个紧密间隔的短链的基本氨基酸（双链）。尽管典型NLSs的长度很短，只有4或5个氨基酸，但它们在细胞质中与NLS受体的输入蛋白家族成员（也称为核细胞蛋白）进行高亲和力相互作用。进口蛋白作为载体，将相互作用的货物定位到细胞核。货物/载体配合物与核孔复合物组分的相互作用导致核输入。

Many proteins are precisely targeted to particular sub-cellular compartments by specific localization signals. Nuclear import of proteins is typically mediated by interaction with soluble cytosolic receptor proteins via nuclear localization signals (NLSs). Canonical NLSs contain either a short stretch of basic amino acids (monopartite) or two closely spaced short stretches of basic amino acids (bipartite). Despite the short length of canonical NLSs, which are as little as 4 or 5 amino acids in length, they make high affinity interactions in the cytosol with members of the importin family of NLS receptors (also known as karyopherins). Importins function as carriers to direct localization of the interacting cargo to the nucleus. The interaction of cargo/carrier complexes with components of the nuclear pore complex leads to nuclear import.