nucleolien

Nucleolien is a term used in cellular biology to refer to a class of nucleolar phosphoproteins, with nucleolin being the most abundant and well studied member. In humans, the protein is encoded by the NCL gene and is a central component of the nucleolus, the subnuclear structure where ribosomal RNA (rRNA) transcription, processing, and ribosome assembly take place. Nucleolien proteins are highly conserved across eukaryotes and are characterized by a tripartite structure: an acidic N-terminal domain, RNA recognition motifs in the central region, and a glycine- and arginine-rich C-terminal GAR domain. This architecture supports strong RNA binding and interactions with ribosomal and non-ribosomal factors.

Functions: They participate in RNA polymerase I-driven transcription of rRNA, early pre-rRNA processing, stabilization and export of ribosomal subunits, and regulation of mRNA turnover and translation. They also participate in chromatin remodeling, DNA replication, and the cellular stress response, and can shuttle between the nucleolus, the nucleus, and the cytoplasm.

Regulation and clinical relevance: Nucleolien activity is regulated by phosphorylation and cellular signaling pathways; expression levels often change during cell proliferation. Overexpression or mislocalization of nucleolin is observed in several cancers and other diseases, making it a potential biomarker or therapeutic target. Nucleolien also interacts with viral components and host factors during infection.