A novel Ded1-like RNA helicase interacts with the Y-box protein ctYB-1 in nuclear mRNP particles and in polysomes.
We have characterized a novel mRNA-binding protein, designated hrp84, in the dipteran Chironomus tentans and identified it as a DEAD-box RNA helicase. The protein contains the typical helicase core domain, a glycine-rich C-terminal part and a putative nuclear export signal in the N terminus. The protein belongs to the Ded1 subgroup of DEAD-box helicases, which is highly conserved from yeast (Ded1p) to mammals (DDX3). In tissue culture cells, hrp84 is present both in the nucleus and cytoplasm and, as shown by in vivo UV cross-linking, is bound to mRNA in both compartments. Immunoprecipitation experiments revealed that hpr84 is associated with the C. tentans homologue (ctYB-1) of the vertebrate Y-box protein YB-1 both in the nucleus and cytoplasm, and the two proteins also appear together in polysomes. The interaction is likely to be direct as shown by in vitro binding of purified components. We conclude that the mRNA-bound hrp84.ctYB-1 complex is formed in the nucleus and is translocated with mRNA into the cytoplasm and further into polysomes. As both Ded1 and YB-1 are known to regulate the initiation of translation, we propose that the RNA helicase-Y-box protein complex affects the efficiency of mRNA translation, presumably by modulating the conformation of the mRNP template.
Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
Dmitri
D
Nashchekin
Jian
J
Zhao
Neus
N
Visa
Bertil
B
Daneholt
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002683:Chironomidae / Q000201:enzymology*; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D009865:Oocytes / Q000378:metabolism; D011132:Polyribosomes / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D020365:RNA Helicases / Q000737:chemistry* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D014466:Ultraviolet Rays; D051840:Y-Box-Binding Protein 1
D000911:Antibodies, Monoclonal; D022762:CCAAT-Enhancer-Binding Proteins; D003432:Cross-Linking Reagents; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human; D020365:RNA Helicases