Structure and function of the nucleolus

The activity of the ribosomal RNA genes generates a distinct subnuclear str ucture, the nucleolus, which is the site of ribosome biogenesis. The signal s that target proteins and snoRNAs (small nucleolar RNAs) to the nucleolus, the nuclear import of ribosomal proteins, the export of the completed ribo somal subunits and the molecular organization of the nucleolus have been th e subject of intense research during the past year. Evidence is accumulatin g that nucleoli functionally interact with coiled bodies and are also invol ved in the maturation of non-ribosomal RNA species.