Nucleolin is a protein that in humans is encoded by the NCL gene.

Gene

The human NCL gene is located on chromosome 2 and consists of 14 exons with 13 introns and spans approximately 11kb. Intron 11 of the NCL gene encodes a small nucleolar RNA, termed U20.

Function

Nucleolin is the major nucleolar protein of growing eukaryotic cells. It is found associated with intranucleolar chromatin and pre-ribosomal particles. It induces chromatin decondensation by binding to histone H1. It is thought to play a role in pre-rRNA transcription and ribosome assembly. May play a role in the process of transcriptional elongation. Binds RNA oligonucleotides with 5'-UUAGGG-3' repeats more tightly than the telomeric single-stranded DNA 5'-TTAGGG-3' repeats. Nucleolin is also able to act as a transcriptional coactivator with Chicken Ovalbumin Upstream Promoter Transcription Factor II (COUP-TFII).

Clinical significance

Midkine and pleiotrophin bind to cell-surface nucleolin as a low affinity receptor. This binding can inhibit HIV infection. Nucleolin at the cell surface is the receptor for the respiratory syncytial virus (RSV) fusion protein. Interference with the nucleolin–RSV fusion protein interaction has been shown to be therapeutic against RSV infection in cell cultures and animal models.

Interactions

Nucleolin has been shown to interact with: