Abstract
Once thought a mere ribosome factory, the nucleolus has been viewed in recent years as an extremely sensitive gauge of diverse cellular stresses. Emerging concepts in nucleolar biology include the nucleolar stress response (NSR), whereby a series of cell insults have a special impact on the nucleolus. These insults include, among others, ultra-violet radiation (UV), nutrient deprivation, hypoxia and thermal stress. While these stresses might influence nucleolar biology directly or indirectly, other perturbances whose origin resides in the nucleolar biology also trigger nucleolar and systemic stress responses. Among the latter, we find mutations in nucleolar and ribosomal proteins, ribosomal RNA (rRNA) processing inhibitors and ribosomal DNA (rDNA) transcription inhibition. The p53 protein also mediates NSR, leading ultimately to cell cycle arrest, apoptosis, senescence or differentiation. Hence, NSR is gaining importance in cancer biology. The nucleolar size and ribosome biogenesis, and how they connect with the Target of Rapamycin (TOR) signalling pathway, are also becoming important in the biology of aging and cancer. Simple model organisms like the budding yeast Saccharomyces cerevisiae, easy to manipulate genetically, are useful in order to study nucleolar and rDNA structure and their relationship with stress. In this review, we summarize the most important findings related to this topic.
Highlights
A membraneless compartment inside the nucleus of eukaryotic cells was observed for the first time by Fontana in 1781 “corps oviforme”, and described by Valentin in 1836 [1]
These special ribosomal RNA (rRNA) genes are in multiple copies per genome since rRNAs are required in large amounts and they cannot be amplified like proteins during translation
Among cell cycle regulators that control ribosomal DNA array (rDNA) morphology at this stage we find the Polo Like Kinase 1 ortholog
Summary
A membraneless compartment inside the nucleus of eukaryotic cells was observed for the first time by Fontana in 1781 “corps oviforme”, and described by Valentin in 1836 [1]. We are mostly leaving out of this review the long-term effects that clastogenic and aneugenic stresses can cause on the rDNA structure, which can have a great and sustained impact on the nucleolar morphology. The connections between these stresses, the rDNA/nucleolus, cancer and aging deserve by itself a deep and updated review in the future. The second concept, chronological aging, is the length of time a population of yeast cells remains viable in a nondividing state following nutrient deprivation [13,14] Both terms are usually referred as replicative life span and chronological life span based on the assays developed to measure them [15]. We will explain very briefly the evidences for the nucleolar size in relation to cancer and aging
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
