Nucleolin

Nucleolin is a ubiquitous, nonhistone nucleolar phosphoprotein of exponentially growing eukaryotic cells and is present in abundance at the dense fibrillar and granular regions of nucleolus. Intact nucleolin is the major species and represents 5% of nucleolar protein in actively dividing cells.

Nucleolin is an abundant, 106 kDa nucleolar phosphoprotein that is a major protein in actively dividing cells. The stability of nucleolin is heavily cell proliferation-dependent, as nucleolin antibody studies have shown that degraded forms are relatively abundant in quiescent non-dividing cells, while nonexist in actively dividing cells.

Nucleolin is a multifunctional phosphoprotein ubiquitously distributed in the nucleolus, nucleus and cytoplasm of the cell. Nucleolin has a bipartite nuclear localization signal sequence and is conserved across the species. Nucleolin levels are expressed in abundance in exponentially growing cells and it regulates various aspects of DNA and RNA metabolism, chromatin structure, rDNA transcription, rRNA maturation, cytokinesis, nucleogenesis, cell proliferation and growth (1).