Nucleolin, which is identical to human DNA helicase IV, is a major nucleolar phosphoprotein which is associated with preribosomal RNA and is implicated in the early stage of preribosomal RNP assembly and processing. This 100 kDa protein has three major domains: a N-terminal domain comprised of long acidic stretches interspersed with basic repeats, similar to the structure of a high mobility group-type protein, a central domain that contains four RNA binding elements, a C-terminal domain approximately 85 amino acids long that is rich in glycine, arginine, and phenylalanine residues. Nucleolin fluctuates in parallel to DNA synthesis; intact 100 kDa protein is the major species in actively dividing cells, whereas the degraded forms are relativley abundant in nondividing cells. Nucleolin can unwind RNA-RNA duplexes, as well as DNA-DNA and DNA-RNA duplexes. Nucleolin also interacts directly with DNA topoisomerase I. It is located mainly in dense fibrillar regions of the nucleolus. Nucleolin is the major nucleolar protein of growing eukaryotic cells. It is found associated with intranucleolar chromatin and preribosomal particles. It induces chromatin decondensation by binding to histone H1. It is thought to play a role in pre-rRNA transcription and ribosome assembly. It interacts with APTX and contains 4 RNA recognition motif (RRM) domains.
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Protein Aliases: C23; FLJ45706; FLJ59041; Nucleolin; Protein C23
Gene Aliases: B530004O11Rik; C23; D0Nds28; D1Nds28; NCL; Nuc; Nucl
Molecular Function: ribosomal protein