title: Ddx42p--a human DEAD box protein with RNA chaperone activities.
abstract: The human gene ddx42 encodes a human DEAD box protein highly homologous to the p68 subfamily of RNA helicases. In HeLa cells, two ddx42 poly(A)+ RNA species were detected both encoding the nuclear localized 938 amino acid Ddx42p polypeptide. Ddx42p has been heterologously expressed and its biochemical properties characterized. It is an RNA binding protein, and ATP and ADP modulate its RNA binding affinity. Ddx42p is an NTPase with a preference for ATP, the hydrolysis of which is enhanced by various RNA substrates. It acts as a non-processive RNA helicase. Interestingly, RNA unwinding by Ddx42p is promoted in the presence of a single-strand (ss) binding protein (T4gp32). Ddx42p, particularly in the ADP-bound form (the state after ATP hydrolysis), also mediates efficient annealing of complementary RNA strands thereby displacing the ss binding protein. Ddx42p therefore represents the first example of a human DEAD box protein possessing RNA helicase, protein displacement and RNA annealing activities. The adenosine nucleotide cofactor bound to Ddx42p apparently acts as a switch that controls the two opposing activities: ATP triggers RNA strand separation, whereas ADP triggers annealing of complementary RNA strands.
authors.affiliation: FR 2.3 Medical Biochemistry and Molecular Biology, Theoretical Medicine, University of the Saarland, D-66421 Homburg, Germany. heike.uhlmann.schiffler@uniklinikum-saarland.de
authors.forename: Heike
authors.initials: H
authors.lastname: Uhlmann-Schiffler
authors.forename: Carolin
authors.initials: C
authors.lastname: Jalal
authors.forename: Hans
authors.initials: H
authors.lastname: Stahl
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D053487:DEAD-box RNA Helicases; D006801:Humans; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D043583:Nucleoside-Triphosphatase / Q000378:metabolism; D011494:Protein Kinases / Q000737:chemistry; D012313:RNA / Q000378:metabolism*; D020365:RNA Helicases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D018832:Molecular Chaperones; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D017413:Ribonucleoprotein, U2 Small Nuclear; D000244:Adenosine Diphosphate; D012313:RNA; D000255:Adenosine Triphosphate; D011494:Protein Kinases; C408625:DDX42 protein, human; C506749:Ddx5 protein, human; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases