A novel DNA-binding domain in the Shrunken initiator-binding protein (IBP1).
South-western screening of lambda gt11 expression library with a fragment of the Shrunken promoter containing the initiator element resulted in cloning of a novel maize gene. The encoded initiator-binding protein (IBP1) interacts at the transcription start site of the Shrunken promoter. Analysis of the 680 amino acid (aa) long polypeptide revealed a novel bipartite DNA-binding domain at the carboxyl terminus. In its amino-terminal part, it is weakly related to Myb R-repeats but the following basic region is also essential for DNA binding. A region of similarity to the conserved 2.1 and 2.2 motifs in bacterial sigma-factors is located close to the IBP1 amino terminus. Two putative nuclear localization signals are compatible with the presence of antigenically related polypeptides in nuclear protein extracts. The IBP1 gene was mapped to the long arm of chromosome 9 (9L095); a second highly related gene IBP2 is located on the short arm of chromosome 1 (1S014). Both genes encode proteins sharing 93% similarity and are transcribed with similar activity in different plant organs. A small 82 nucleotide intron in the IBP2 transcript is found unspliced to a variable degree in different tissues. Translation of this incompletely processed transcript would result in a truncated amino-terminal polypeptide lacking the DNA-binding domain.
Lugert
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Institut für Genetik der Universität zu Köln, Germany.
Werr
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D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D015153:Blotting, Western; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000737:chemistry; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics*; D051599:Glucose-1-Phosphate Adenylyltransferase; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000235:genetics*; D010940:Plant Proteins; D012150:Polymorphism, Restriction Fragment Length; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012326:RNA Splicing; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D003313:Zea mays / Q000235:genetics*
D004268:DNA-Binding Proteins; C088757:IBP1 protein, Zea mays; C088758:IBP2 protein, Zea mays; D010940:Plant Proteins; D009713:Nucleotidyltransferases; D051599:Glucose-1-Phosphate Adenylyltransferase