Discrete foci containing RNAse A are found in nucleoli of HeLa cells after aging in culture

Abstract

We have studied by means of ultrastructural immunocytochemistry the localization of RNase A in nuclei of HeLa cells in control conditions and following cell ageing in culture. We have found that roundish, electron dense foci, which contain a significant amount of RNase A, can be detected within nucleoli of aged cells. These bodies also contain RNA and lack ribosomal S3 proteins, and may represent either simple storage sites or areas where RNA degradation takes place.

On the future contents of a small journal of histochemistry

“…30,32,94,96 In this perspective, it becomes primarily important to discriminate cells in the different phases of proliferation, differentiation, aging and death, through specific molecular markers: multiple immunocytochemical techniques were widely applied to this aim. 24,31,38,43,45,97–99 A manuscript only was devoted to plant cell development, 100 and this confirms that histochemistry is still relatively poorly used by plant biologists in their research: actually, in the last three years, only 30 papers have been published, in which histochemical techniques have been used in investigations on plant cell biology (source: www.scopus.com). In recent years, connective tissues and, in particular, bone and cartilage have become increasingly popular subjects for the authors of the European Journal of Histochemistry .…”

“…23–27 Most of these studies were performed by light (essentially conventional or confocal fluorescence) microscopy, but electron microscopy and ultrastructural immunohistochemistry has also been used for investigating functional changes in cells from different tissues or under different experimental conditions. 28–37 To localize specific nuclear components, multiple immunohistochemical techniques and quantitative analyses of the immunogold labelling have been utilized, 38 and this approach proved to be especially appropriate to detect the alteration in transcription and splicing which characterizes specific diseases. 24,31,39 …”

Immunofluorescent localization of ubiquitin and proteasomes in nucleolar vacuoles of soybean root meristematic cells

“…58 That is why the presence of ubiquitin in a nucleolus does not necessarily mean that degradation of ubiquitinated proteins takes place in a nucleolus, however it may indicate that nucleoli, precisely the nucleolar vacuoles, may not merely be useless empty space formed in active nucleoli as a consequence of intensive transport of pre-ribosomal particles out of the nucleoli, but they could be the site of temporary sequestration or storage of the UPS components or ubiquitin conjugates as well as other biochemical cellular components in plant cells, 59 similarly as different discrete, focal regions in animal nucleoli are used as storage compartments for certain enzymatic and regulatory proteins, which can be released in a regulated manner to exert their function elsewhere. 60,61 …”

Functional ultrastructure of the plant nucleolus

“…Moreover, some nucleolar functions result from the fact that nucleoli are the sites of temporal inactivation through nucleolar sequestration of enzymatic or regulatory proteins associated with those functions (Table 4 ). Then, they are released at the given situation at the right time in order to exert the established effect (Olson et al 2000 ; Visintin and Amon 2000 ; Costanzo et al 2011 ; Audas et al 2012 ). Large portion of new and interesting information, also referring to the molecular level, focused mainly on mammalian nucleoli as reactors for ribosome production as well as structures playing noncanonical functions Readers will find in some extensive reviews (Pederson 1998 , 2010 ; Olson 2004 ; Raška et al 2006b ; Boisvert et al 2007 ; Brown and Shaw 2008 ; Sirri et al 2008 ; Hernandez-Verdun et al 2010 ; Shaw and Brown 2012 ).…”

“…Some of these functions use the same conventional nucleolar compartments as ribosome biosynthesis does. Nevertheless, maintenance of the local concentration of specific macromolecules at various sites of nucleolar territory pointed out to these sites as additional nucleolar domains playing defined functions (Costanzo et al 2011 ; Hutten et al 2011 ; Latonen et al 2011 ).…”