A human polyadenylation factor is a G protein beta-subunit homologue.
Cleavage stimulation factor (CstF) is one of the multiple factors required for polyadenylation of mammalian pre-mRNAs in vitro. We have shown previously that this factor is composed of three distinct subunits of 77, 64, and 50 kDa, and that the 64-kDa subunit can be UV-cross-linked to RNA in a polyadenylation signal (AAUAAA)-dependent manner. By molecular cloning, the 64-kDa subunit was shown to contain a ribonucleoprotein-type RNA binding domain and a novel repeat structure. To study the functions of the other subunits, we have now isolated cDNAs encoding the 50-kDa subunit of human CstF. This subunit shares extensive homology with mammalian G protein beta-subunits and has a characteristic repeat structure (transducin repeat), in which an approximately 44-amino acid-long sequence is repeated seven times. To our knowledge, the 50-kDa subunit is the first example of a functional beta-subunit-like protein in vertebrates. Possible roles of the transducin repeat, both in CstF function specifically and in other beta-subunit homologues more generally, are discussed.
Department of Biological Sciences, Columbia University, New York, New York 10027.
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Takagaki
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Manley
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D003001:Cloning, Molecular; D019204:GTP-Binding Proteins / Q000235:genetics*; D015723:Gene Library; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009838:Oligodeoxyribonucleotides; D011061:Poly A / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid; D039221:mRNA Cleavage and Polyadenylation Factors
D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D039221:mRNA Cleavage and Polyadenylation Factors; D011061:Poly A; D019204:GTP-Binding Proteins