title: Mitochondrial genome-encoded ATPase subunit 6+8 mRNA increases in human hepatoblastoma cells in response to nonfatal cold stress.
abstract: Cellular responses to cold stress have not been well clarified, compared with heat shock responses, especially in mammalian cells. We investigated cold-stress responses in human hepatoblastoma cells (HepG2) exposed to a nonfatal temperature of 17 degrees C. Under the condition, RNA and protein syntheses in the cells were highly, but incompletely, depressed and cell growth was impaired. A cDNA subtraction method was used to isolate mRNAs for which the levels were increased in cold-stressed cells compared with cells cultured at 37 degrees C. A transcript isolated by the screening was identified as ATPase subunit 6+8 mRNA that encodes components of a mitochondrial ATPase complex and that is transcribed from a mitochondrial genome. The copy number of the mitochondrial genome in cells was not changed by cold stress. Thus, HepG2 cells were treated with various concentrations of actinomycin D and chloramphenicol to assess the effects of transcriptional and translational reduction on the increased level of the ATPase subunit 6+8 mRNA. The mRNA level was increased in cells treated with low concentrations of the RNA or protein synthesis inhibitors. These results indicate that the increase in ATPase subunit 6+8 mRNA stimulated by cold stress could be mediated by a partial decline of transcription and/or translation in the cells. In addition, the degradation of ATPase subunit 6+8 mRNA was suppressed in cold-stressed cells compared with that in 37 degrees C-cultured cells. This result implies that posttranscriptional regulation is also involved in the cold-stimulated increase in ATPase subunit 6+8 mRNA in HepG2 cells.
authors.affiliation: Japan Science and Technology Corporation, Kawaguchi, 332-0012, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ohsaka
authors.forename: S
authors.initials: S
authors.lastname: Ohgiya
authors.forename: T
authors.initials: T
authors.lastname: Hoshino
authors.forename: K
authors.initials: K
authors.lastname: Ishizaki
mesh_terms: D017209:Apoptosis; D003080:Cold Temperature; D004261:DNA Replication; D018076:DNA, Complementary / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D004790:Enzyme Induction; D015972:Gene Expression Regulation, Neoplastic; D018197:Hepatoblastoma / Q000201:enzymology / Q000473:pathology*; D006801:Humans; D008113:Liver Neoplasms / Q000201:enzymology / Q000473:pathology*; D006180:Proton-Translocating ATPases / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis*; D012334:RNA, Neoplasm / Q000096:biosynthesis*; D013312:Stress, Physiological / Q000235:genetics / Q000378:metabolism; D013382:Subtraction Technique; D014407:Tumor Cells, Cultured / Q000201:enzymology
chemical_list: D018076:DNA, Complementary; D004272:DNA, Mitochondrial; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D006180:Proton-Translocating ATPases