title: Cloning of a cDNA encoding a novel importin-alpha homologue, Qip1: discrimination of Qip1 and Rch1 from hSrp1 by their ability to interact with DNA helicase Q1/RecQL.
abstract: We isolated two cDNA clones encoding human proteins which interact with DNA helicase Q1/RecQL, a human homologue of Eschelichia coli RecQ protein, by two-hybrid screening. One of these proteins, named Qip1, was a novel protein homologous to the nuclear localization signal (NLS) receptor importin-alpha, and the other was the known protein Rch1, which is also a homologue of importin-alpha. DNA helicase Q1 in human cell lysates was coprecipitated with bacterially expressed Qip1 and Rch1 fused with glutathione-S-transferase with glutathione Sepharose beads, confirming the interaction between these proteins and DNA helicase Q1. Two-hybrid experiments revealed that Qip1 interacted with the NLS of SV40 T antigen similar to Rch1 and hSrp1. In addition, interaction of the putative NLS in DNA helicase Q1 with Qip1 and Rch1 but not with hSrp1 was confirmed by the two-hybrid system.
authors.affiliation: Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Seki
authors.forename: S
authors.initials: S
authors.lastname: Tada
authors.forename: T
authors.initials: T
authors.lastname: Katada
authors.forename: T
authors.initials: T
authors.lastname: Enomoto
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D028884:Karyopherins; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011485:Protein Binding; D053484:RecQ Helicases; D012441:Saccharomyces cerevisiae / Q000737:chemistry; D012685:Sepharose; D016415:Sequence Alignment; D017421:Sequence Analysis; D028901:alpha Karyopherins
chemical_list: D002352:Carrier Proteins; C106259:KPNA4 protein, human; D028884:Karyopherins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D028901:alpha Karyopherins; C087978:karyopherin alpha 2; D012685:Sepharose; D000251:Adenosine Triphosphatases; C506731:RECQL4 protein, human; D004265:DNA Helicases; D053484:RecQ Helicases; D005978:Glutathione