title: Heat shock protein 70 inhibits hydrogen peroxide-induced nucleolar fragmentation via suppressing cleavage and down-regulation of nucleolin.
abstract: It has been reported that nucleolar fragmentation is a part of the overall apoptotic morphology, however, it is currently obscure whether and how nucleolar fragmentation can be induced by hydrogen peroxide (H(2)O(2)) and heat shock protein 70 (Hsp70) can prevent nucleolar fragmentation. To dissect these two questions, C(2)C(12) myogenic cells and immortalized mouse embryonic fibroblasts (MEFs) with heat shock transcriptional factor 1 (HSF1) null mutation were treated with heat shock response (HS) (42.5 ± 0.5°C for 1 h and recovery at 37°C for 24 h) and then were insulted with 0.5 mmol/L H(2)O(2). Morphological changes of nucleoli were observed under contrast microscope or electronic microscope. It was found that (1) stimulation with H(2)O(2)-induced nucleolar fragmentation by mediating cleavage and down-regulation of nucleolar protein, nucleolin in C(2)C(12) myocytes and MEFs; (2) HS suppressed nucleolar fragmentation by inducing the expression of Hsp70 in an HSF1-dependent manner as indicated by assays of transfection with Hsp70 antisense oligonucleotides (AS-ONs) or recombinant plasmids of full-length Hsp70 cDNA; (3) protection of Hsp70 against nucleolar fragmentation was related to its accumulation in nucleolus mediated by nuclear localization sequence and its inhibition against cleavage and down-regulation of nucleolin. These results suggested that H(2)O(2)-induced nucleolar fragmentation and HS or Hsp70 inhibit H(2)O(2)-induced nucleolar fragmentation through the translocation of Hsp70 into nucleolar and its protection against impairment of nucleolin.
authors.affiliation: Department of Pathophysiology, Xiangya School of Medicine, Central South University, 110 Xiangya Road, Changsha, Hunan 410008, People's Republic of China.
authors.forename: Kangkai
authors.initials: K
authors.lastname: Wang
authors.forename: Gonghua
authors.initials: G
authors.lastname: Deng
authors.forename: Guangwen
authors.initials: G
authors.lastname: Chen
authors.forename: Meidong
authors.initials: M
authors.lastname: Liu
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Yi
authors.forename: Tubao
authors.initials: T
authors.lastname: Yang
authors.forename: Daniel R
authors.initials: DR
authors.lastname: McMillan
authors.forename: Xiangzhong
authors.initials: X
authors.lastname: Xiao
mesh_terms: D000818:Animals; D002460:Cell Line; D002466:Cell Nucleolus / Q000187:drug effects* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D000076249:Heat Shock Transcription Factors; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D051379:Mice; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D000097796:Nucleolin
chemical_list: D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D006861:Hydrogen Peroxide; D016376:Oligonucleotides, Antisense; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D000097796:Nucleolin; C490017:Hsf1 protein, mouse