The GA motif: an RNA element common to bacterial antitermination systems, rRNA, and eukaryotic RNAs.
Two different transcription termination control mechanisms, the T box and S box systems, are used to regulate transcription of many bacterial aminoacyl-tRNA synthetase, amino acid biosynthesis, and amino acid transport genes. Both of these regulatory mechanisms involve an untranslated mRNA leader region capable of adopting alternate structural conformations that result in transcription termination or transcription elongation into the downstream region. Comparative analyses revealed a small RNA secondary structural element, designated the GA motif, that is highly conserved in both T box and S box leader sequences. The motif consists of two short helices separated by an asymmetric internal loop, with highly conserved GA dinucleotide sequences on either side of the internal loop. Site-directed mutagenesis of this motif in model T and S box leader sequences indicated that it is essential for transcriptional regulation in both systems. This motif is similar to the binding site of yeast ribosomal protein L30, the Snu13p binding sites found in U4 snRNA and box C/D snoRNAs, and two elements in 23S rRNA.
Winkler
W C
WC
Department of Microbiology, The Ohio State University, Columbus 43210, USA.
Grundy
F J
FJ
Murphy
B A
BA
Henkin
T M
TM
D001419:Bacteria / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D012333:RNA, Messenger / Q000378:metabolism; D012335:RNA, Ribosomal / Q000235:genetics*; D012338:RNA, Ribosomal, 23S / Q000737:chemistry; D012342:RNA, Small Nuclear / Q000737:chemistry; D020537:RNA, Small Nucleolar / Q000737:chemistry; D012269:Ribosomal Proteins / Q000737:chemistry; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000378:metabolism
D005656:Fungal Proteins; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D012338:RNA, Ribosomal, 23S; D012342:RNA, Small Nuclear; D020537:RNA, Small Nucleolar; D012269:Ribosomal Proteins; C405482:U4 small nuclear RNA; C035201:ribosomal protein L30; D001616:beta-Galactosidase