title: Comparison of the sequence and structure of transcription factor IIIA from Bufo americanus and Rana pipiens.
abstract: Amino acid (aa) sequences of transcription factor IIIA (TFIIIA) from the toad, Bufo americanus, and the grass frog, Rana pipiens, were determined by cDNA cloning and DNA sequencing. The 3'-untranslated regions of the cDNAs reveal that the TFIIIA gene polyadenylation signal is ATTAAA, rather than the conventional AATAAA. The B. americanus and R. pipiens proteins share about 60% aa sequence homology with each other and with Xenopus laevis TFIIIA. Although these results indicate that TFIIIA has more sequence variation than other DNA-binding proteins, a number of conserved features are evident and of likely functional significance. These include potential guanine nucleotide-binding sites at arginines in zinc fingers (ZnF) II, V, and IX, acidic residues between metal-coordinating cysteines, and a basic region in the C-terminal tail possibly involved in transcription promotion. Sequence similarity also exists in an aa stretch bridging the ninth ZnF and C-terminal tail of both TFIIIA and the 5S RNA-binding protein, p43. DNase I protection analyses demonstrate that B. americanus and R. pipiens TFIIIA interact with the internal control region (ICR) of the Xenopus borealis 5S RNA-encoding gene (5S) in different manners: the B. americanus interaction is similar to X. laevis TFIIIA, protecting the entire 5S gene ICR (nt +96 to +43) from DNase I digestion, whereas the R. pipiens TFIIIA strongly protects the ICR from nt +96 up to +78 and less strongly from +78 to +43. Possibly accounting for the binding differences observed, R. pipiens and R. catesbeiana oocyte 5S RNAs (and by inference 5S genes) were found to contain a G or U at nt position 50 while B. americanus, X. laevis, and other eukaryotic 5S RNAs have an A in the analogous position (nt 53 in generalized eukaryotic structure).
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City 73190.
authors.forename: C J
authors.initials: CJ
authors.lastname: Gaskins
authors.forename: J F
authors.initials: JF
authors.lastname: Smith
authors.forename: M K
authors.initials: MK
authors.lastname: Ogilvie
authors.forename: J S
authors.initials: JS
authors.lastname: Hanas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002025:Bufonidae; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics* / Q000302:isolation & purification; D008961:Models, Structural; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012341:RNA, Ribosomal, 5S / Q000235:genetics*; D011894:Rana pipiens; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D012341:RNA, Ribosomal, 5S; D011994:Recombinant Proteins; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors; D004247:DNA