title: Nucleolar aggresomes mediate release of pericentric heterochromatin and nuclear destruction of genotoxically treated cancer cells.
abstract: The role of the nucleolus and autophagy in maintenance of nuclear integrity is poorly understood. In addition, the mechanisms of nuclear destruction in cancer cells senesced after conventional chemotherapy are unclear. In an attempt to elucidate these issues, we studied teratocarcinoma PA1 cells treated with Etoposide (ETO), focusing on the nucleolus. Following treatment, most cells enter G2 arrest, display persistent DNA damage and activate p53, senescence, and macroautophagy markers. 2-5 µm sized nucleolar aggresomes (NoA) containing fibrillarin (FIB) and damaged rDNA, colocalized with ubiquitin, pAMPK, and LC3-II emerge, accompanied by heterochromatin fragments, when translocated perinuclearly. Microscopic counts following application of specific inhibitors revealed that formation of FIB-NoA is dependent on deficiency of the ubiquitin proteasome system coupled to functional autophagy. In contrast, the accompanying NoAs release of pericentric heterochromatin, which exceeds their frequency, is favored by debilitation of autophagic flux. Potential survivors release NoA in the cytoplasm during rare mitoses, while exit of pericentric fragments often depleted of H3K9Me3, with or without encompassing by NoA, occurs through the nucleolar protrusions and defects of the nuclear envelope. Foci of LC3-II are accumulated in the nucleoli undergoing cessation of rDNA transcription. As an origin of heterochromatin fragmentation, the unscheduled DNA synthesis and circular DNAs were found in the perinucleolar heterochromatin shell, along with activation and retrotransposition of ALU elements, colocalized with 45S rDNA in NoAs. The data indicate coordination of the basic nucleolar function with autophagy regulation in maintenance of the integrity of the nucleolus associated domains secured by inactivity of retrotransposons.
authors.affiliation: a Latvian Biomedical Research & Study Centre , Riga , Latvia.
authors.forename: Kristine
authors.initials: K
authors.lastname: Salmina
authors.affiliation: a Latvian Biomedical Research & Study Centre , Riga , Latvia.
authors.forename: Anda
authors.initials: A
authors.lastname: Huna
authors.affiliation: a Latvian Biomedical Research & Study Centre , Riga , Latvia.
authors.forename: Inna
authors.initials: I
authors.lastname: Inashkina
authors.affiliation: b Botanical Institute AS CR , Czech Academy of Science , Prague, Czech Republic.
authors.forename: Alexander
authors.initials: A
authors.lastname: Belyayev
authors.affiliation: a Latvian Biomedical Research & Study Centre , Riga , Latvia.
authors.forename: Jekabs
authors.initials: J
authors.lastname: Krigerts
authors.affiliation: b Botanical Institute AS CR , Czech Academy of Science , Prague, Czech Republic.
authors.forename: Ladislava
authors.initials: L
authors.lastname: Pastova
authors.affiliation: a Latvian Biomedical Research & Study Centre , Riga , Latvia.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Vazquez-Martin
authors.affiliation: a Latvian Biomedical Research & Study Centre , Riga , Latvia.
authors.forename: Jekaterina
authors.initials: J
authors.lastname: Erenpreisa
mesh_terms: D001343:Autophagy / Q000187:drug effects / Q000235:genetics; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D016922:Cellular Senescence / Q000187:drug effects / Q000235:genetics; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D004249:DNA Damage; D004275:DNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D005047:Etoposide / Q000633:toxicity; D006570:Heterochromatin / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D009153:Mutagens / Q000633:toxicity*; D018626:Retroelements / Q000187:drug effects / Q000235:genetics
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004275:DNA, Ribosomal; D006570:Heterochromatin; D009153:Mutagens; D018626:Retroelements; C047458:fibrillarin; D005047:Etoposide
keywords: ALU retrotransposition; LADs; NADs; aggresome; autophagy; cellular senescence; nucleolus; pericentric fragments; rRNA transcription; ubiquitin-proteasome