Colocalization of coilin and nucleolar proteins in Cajal body-like structures of micronucleated PtK2 cells

Abstract

Cajal bodies (CB) are ubiquitous nuclear structures involved in the biogenesis of small nuclear ribonucleoproteins and show narrow association with the nucleolus. To identify possible relationships between CB and the nucleolus, the localization of coilin, a marker of CB, and of a set of nucleolar proteins was investigated in cultured PtK 2 cells undergoing micronucleation. Nocodazol-induced micronucleated cells were examined by double indirect immunofluorescence with antibodies against coilin, fibrillarin, NOR-90/hUBF, RNA polymerase I, PM/Scl, and To/Th. Cells were imaged on a BioRad 1024-UV confocal system attached to a Zeiss Axiovert 100 microscope. Since PtK 2 cells possess only one nucleolus organizer region, micronucleated cells presented only one or two micronuclei containing nucleolus. By confocal microscopy we showed that in most micronuclei lacking a typical nucleolus a variable number of round structures were stained by antibodies against fibrillarin, NOR-90/hUBF protein, and coilin. These bodies were regarded as CB-like structures and were not stained by anti-PM/Scl and anti-To/Th antibodies. Anti-RNA polymerase I antibodies also reacted with CB-like structures in some micronuclei lacking nucleolus. The demonstration that a set of proteins involved in RNA/RNP biogenesis, namely coilin, fibrillarin, NOR-90/hUBF, and RNA polymerase I gather in CB-like structures present in nucleolidevoid micronuclei may contribute to shed some light into the understanding of CB function.

Potentials and capabilities of the Extracellular Vesicle (EV) Array

“…This suggests the possibility that it is possible to detect normally intracellular and even nuclear located proteins on the surface of cells and therefore also on the surface of their exosomes. This possibility is endorsed by the fact that the nuclear protein coilin (12), as previously mentioned, was measured in different levels in the tested donors, which could argue against unspecific binding. Furthermore, the ESCRT protein TSG101 has shown great potential as one of the more important proteins in a 30‐marker model able to distinguish non‐small cell lung cancer patients from non‐cancer patients by phenotyping their plasma exosomes (2).…”

The Cajal body and the nucleolus: “In a relationship” or “It's complicated”?

“…A study using prolonged nocodazole treatment to induce micronucleation of rat-kangaroo kidney cells reported a number of micronuclei containing CB-like structures but not nucleoli. 125 In pigeon oocytes, which lack functional nucleoli, CB-like structures, containing coilin and snRNPs but lacking fibrillarin, have been detected, 126 suggesting that CBs may, on occasion, be independent from nucleoli.…”

Investigations into the regulation of histone H2B monoubiquitination

“…In micronucleated cells coilin was shown to be co-localized with nucleolar components such as fibrillarin, NOR-90 and RNA polymerase I. The functional role of such a protein localization shift remains unclear (Silva et al, 2004) .…”