nuclear pore

The nuclear pore is a protein-lined channel in the nuclear envelope that regulates the transportation of molecules between the nucleus and the cytoplasm. In eukaryotic cells, the nucleus is separated from the cytoplasm and surrounded by a nuclear envelope. This envelope safeguards the DNA contained in the nucleus. In spite of this barrier, there is still communication between the nucleus and the cytoplasm. This communication is regulated by the nuclear pores.

Each nuclear pore is a large complex of proteins that allows small molecules and ions to freely pass, or diffuse, into or out of the nucleus. Nuclear pores also allow necessary proteins to enter the nucleus from the cytoplasm if the proteins have special sequences that indicate they belong in the nucleus. These sequence tags are known as nuclear localization signals. Similarly, RNA transcribed in the nucleus and proteins that are destined to enter the cytoplasm have nuclear export sequences that tag them for release through the nuclear pores.