The U1 small nuclear ribonucleoprotein (snRNP) 70K protein is transported independently of U1 snRNP particles via a nuclear localization signal in the RNA-binding domain.
Expression of the recombinant human U1-70K protein in COS cells resulted in its rapid transport to the nucleus, even when binding to U1 RNA was debilitated. Deletion analysis of the U1-70K protein revealed the existence of two segments of the protein which were independently capable of nuclear localization. One nuclear localization signal (NLS) was mapped within the U1 RNA-binding domain and consists of two typically separated but interdependent elements. The major element of this NLS resides in structural loop 5 between the beta 4 strand and the alpha 2 helix of the folded RNA recognition motif. The C-terminal half of the U1-70K protein which was capable of nuclear entry contains two arginine-rich regions, which suggests the existence of a second NLS. Site-directed mutagenesis of the RNA recognition motif NLS demonstrated that the U1-70K protein can be transported independently of U1 RNA and that its association with the U1 small nuclear ribonucleoprotein particle can occur in the nucleus.
Romac
J M
JM
Department of Microbiology, Duke University Medical Center, Durham, North Carolina 27710.
Graff
D H
DH
Keene
J D
JD
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D000939:Epitopes / Q000032:analysis; D006801:Humans; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000032:analysis; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear / Q000302:isolation & purification / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014162:Transfection
D000939:Epitopes; D010446:Peptide Fragments; D012333:RNA, Messenger; D011994:Recombinant Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear