title: A temperature-sensitive mutant of the mammalian RNA helicase, DEAD-BOX X isoform, DBX, defective in the transition from G1 to S phase.
abstract: ts ET24 cells are a novel temperature-sensitive (ts) mutant for cell proliferation of hamster BHK21 cells. The human genomic DNA which rescued the temperature-sensitive lethality of ts ET24 cells was isolated and screened for an open reading frame in the deposited human genomic library. X chromosomal DBX gene encoding the RNA helicase, DEAD-BOX X isoform, which is homologous to yeast Ded1p, was found to be defective in this mutant. The single point mutation (P267S) was localized between the Motifs I and Ia of the hamster DBX of ts ET24 cells. At the nonpermissive temperature of 39.5 degrees C, ts ET24 cells were arrested in the G1-phase and survived for more than 3 days. In ts ET24 cells, total protein synthesis was not reduced at 39.5 degrees C for 24 h, while mRNA accumulated in the nucleus after incubation at 39.5 degrees C for 17 h. The amount of cyclin A mRNA decreased in ts ET24 cells within 4 h after the temperature shift to 39.5 degrees C, consistent with the fact that the entry into the S-phase was delayed by the temperature shift.
authors.affiliation: Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka 812-8582.
authors.forename: Junko
authors.initials: J
authors.lastname: Fukumura
authors.forename: Eishi
authors.initials: E
authors.lastname: Noguchi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sekiguchi
authors.forename: Takeharu
authors.initials: T
authors.lastname: Nishimoto
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D006224:Cricetinae; D019925:Cyclin A / Q000096:biosynthesis; D019926:Cyclin B / Q000096:biosynthesis; D004247:DNA / Q000737:chemistry / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D039561:Eukaryotic Initiation Factor-4E / Q000096:biosynthesis; D016193:G1 Phase / Q000235:genetics* / Q000502:physiology; D005816:Genetic Complementation Test; D015894:Genome, Human; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes; D008969:Molecular Sequence Data; D017354:Point Mutation; D020365:RNA Helicases / Q000235:genetics* / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D016196:S Phase / Q000235:genetics* / Q000502:physiology; D020539:Sequence Analysis, Protein; D013696:Temperature; D014162:Transfection
chemical_list: D019925:Cyclin A; D019926:Cyclin B; D018076:DNA, Complementary; D039561:Eukaryotic Initiation Factor-4E; D007527:Isoenzymes; D012333:RNA, Messenger; D004247:DNA; D020365:RNA Helicases