Nucleolin is a multifunctional protein , which can be divided into three domains with different construction and conditioning various functions. This protein is mainly localized in the nucleoli , but also occurs in karioplazmie beyond, in the cytoplasm and the cell membrane and is able to move between these compartments . The diverse location speaks for his participation in the cell in multiple physiological processes and pathological conditions. However, the main function of nucleolin is involved in rRNA processing from the stage of the organization of rDNA transcription prerybosomowych particles . Nucleolin is involved in changes in chromatin structure , lengthening the primary transcript of rRNA and ribosome maturation . It also demonstrates the ability to include stabilize the mRNA , forming the structure of nucleoli , or participate in the process of apoptosis. Nucleolin has been implicated in carcinogenesis induced by human papilloma virus and affects suppressor proteins and transcription factors . Studies on the expression of nucleolin in breast cancers have shown its relationship with histological type , estrogen receptor expression , cell cycle phases and the presence of metastases in the lymph nodes . In recent years, also highlighted the role of nucleolin localized in the plasma membrane in the penetration of virus particles to the cell. In HIV infection , it may be a potential therapeutic target . Nucleolin also affects the hepatotropic virus replication . An important role of nucleolin in viral infections is also confirmed by the fact of its co-occurrence of multiple virus antigens . The paper discusses the structure of nucleolin , regulation of expression and post-translational modifications and the main functions in the cell. Furthermore shows the latest views on the role of nucleolin in cancer biology and its contribution to viral infections , especially HIV infection and hepatotropic viruses .