核输出串行又称作核输出信号（英语：nuclear export signal，NES）是由四个疏水氨基酸残基组成的蛋白质肽段串行，能将蛋白从细胞核通过核孔复合体核运输到细胞质。与之功能相反的是能将蛋白运入细胞核的核定位串行（英语：nuclear localization signal，NLS）。NES可以被外输蛋白识别并结合。生物信息学分析 NESs found the most common spacing of the hydrophobic residues to be L_xxxL_xxL_xL, where "L" is a hydrophobic residue (often leucine) and "x" is any other amino acid; the spacing of these hydrophobic residues may be explained by examination of known structures that contain an NES, as the critical residues usually lie in the same face of adjacent secondary structures within a protein, which allows them to interact with the exportin. Ribonucleic acid (RNA) is composed of nucleotides, and thus, lacks the nuclear export signal to move out of the nucleus. As a result, most forms of RNA will bind to a protein molecule to form a ribonucleoprotein complex to be exported from the nucleus.

A nuclear export signal (NES) is a short amino acid sequence of 4 hydrophobic residues in a protein that targets it for export from the cell nucleus to the cytoplasm through the nuclear pore complex using nuclear transport. It has the opposite effect of a nuclear localization signal, which targets a protein located in the cytoplasm for import to the nucleus. The NES is recognized and bound by exportins. In silico analysis of known NESs found the most common spacing of the hydrophobic residues to be L_xxxL_xxL_xL, where "L" is a hydrophobic residue (often leucine) and "x" is any other amino acid; the spacing of these hydrophobic residues may be explained by examination of known structures that contain an NES, as the critical residues usually lie in the same face of adjacent secondary structures within a protein, which allows them to interact with the exportin. Ribonucleic acid (RNA) is composed of nucleotides, and thus, lacks the nuclear export signal to move out of the nucleus. As a result, most forms of RNA will bind to a protein molecule to form a ribonucleoprotein complex to be exported from the nucleus.