Sequence-specific DNA recognition by the Myb-like domain of plant telomeric protein RTBP1.
We have identified a rice gene encoding a DNA-binding protein that specifically recognizes the telomeric repeat sequence TTTAGGG found in plants. This gene, which we refer to as RTBP1 (rice telomere-binding protein 1), encodes a polypeptide with a predicted molecular mass of 70 kDa. RTBP1 is ubiquitously expressed in various organs and binds DNA with two or more duplex TTTAGGG repeats. The predicted protein sequence includes a single domain at the C terminus with extensive homology to Myb-like DNA binding motif. The Myb-like domain of RTBP1 is very closely related to that of other telomere-binding proteins, including TRF1, TRF2, Taz1p, and Tbf1p, indicating that DNA-binding domains of telomere-binding proteins are well conserved among evolutionarily distant species. To obtain precise information on the sequence of the DNA binding site recognized by RTBP1, we analyzed the sequence-specific binding properties of the isolated Myb-like domain of RTBP1. The isolated Myb-like domain was capable of sequence-specific DNA binding as a homodimer. Gel retardation analysis with a series of mutated telomere probes revealed that the internal GGGTTT sequence in the two-telomere repeats is critical for binding of Myb-like domain of RTBP1, which is consistent with the model of the TRF1.DNA complex showing that base-specific contacts are made within the sequence GGGTTA. To the best of our knowledge, RTBP1 is the first cloned gene in which the product is able to bind double-stranded telomeric DNA in plants. Because the Myb-like domain appears to be a significant motif for a large class of proteins that bind the duplex telomeric DNA, RTBP1 may play important roles in plant telomere function in vivo.
Yu
E Y
EY
Department of Biology, College of Science, Bioproducts Research Center, Yonsei University, Seoul 120-749, Korea.
Kim
S E
SE
Kim
J H
JH
Ko
J H
JH
Cho
M H
MH
Chung
I K
IK
D000595:Amino Acid Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018628:Gene Dosage; D015723:Gene Library; D017343:Genes, Plant; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics*; D010446:Peptide Fragments / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics; D011485:Protein Binding; D020598:Proto-Oncogene Proteins c-myb; D012091:Repetitive Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D034501:Telomere-Binding Proteins; D035321:Telomeric Repeat Binding Protein 1
D004268:DNA-Binding Proteins; D010446:Peptide Fragments; D010940:Plant Proteins; D020598:Proto-Oncogene Proteins c-myb; D034501:Telomere-Binding Proteins; D035321:Telomeric Repeat Binding Protein 1; C440852:telomere binding protein-1, Oryza sativa