The trimethylguanosine cap structure of U1 snRNA is a component of a bipartite nuclear targeting signal.
The ability of series of U1 snRNAs and U6 snRNAs to migrate into the nucleus of Xenopus oocytes after injection into the cytoplasm was analyzed. The U snRNAs were made either by injecting U snRNA genes into the nucleus of oocytes or, synthetically, by T7 RNA polymerase, incorporating a variety of cap structures. The results indicate that nuclear targeting of U1 snRNA requires both a trimethylguanosine cap structure and binding of at least one common U snRNP protein. Using synthetic U6 snRNAs, it is further demonstrated that the trimethylguanosine cap structure can act in nuclear targeting in the absence of the common U snRNP proteins. These results imply that U snRNP nuclear targeting signals are of a modular nature.
Hamm
J
J
European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany.
Darzynkiewicz
E
E
Tahara
S M
SM
Mattaj
I W
IW
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism*; D005260:Female; D006151:Guanosine / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D009865:Oocytes / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012315:RNA Caps / Q000032:analysis*; D012342:RNA, Small Nuclear / Q000096:biosynthesis / Q000235:genetics*; D015183:Restriction Mapping; D012261:Ribonucleoproteins / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear; D014981:Xenopus
D009687:Nuclear Proteins; D012315:RNA Caps; D012342:RNA, Small Nuclear; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear; D006151:Guanosine; C017778:N(2),N(2),7-trimethylguanosine