Sequence-specific DNA Recognition by the Myb-like Domain of Plant Telomeric Protein RTBP1

Abstract

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 Myblike domain of RTBP1, which is consistent with the model of the TRF1⅐DNA 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 doublestranded 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.

Expression of the Telomeric Repeat Binding Factor Gene NgTRF1 Is Closely Coordinated with the Cell Division Program in Tobacco BY-2 Suspension Culture Cells

“…6B). These results are in line with the previous observations that rice RTBP1 and Arabidopsis AtTBP1 are ubiquitously present in various parts of plants (40,42). To investigate whether NgTRF1 expression is correlated with tissue development, roots were serially dissected according to different developmental stages (sections 1-4), and total RNAs from each section were subjected to RNA gel blot analysis.…”

“…Gel retardation assays showed that the Myb domain of both the rice and Arabidopsis proteins was able to bind to double-stranded, but not single-stranded, plant telomeric DNA (40 -42). The mRNAs for rice RTBP1 and Arabidopsis AtTBP1 were ubiquitously present in all tissues examined (40,42). However, these studies did not provide any information about the physiological roles and developmental regulation patterns of these telomere-related genes.…”

Toward closing rice telomere gaps: mapping and sequence characterization of rice subtelomere regions

“…The complex structure of subtelomere regions with various units of tandem or interspersed repeats has been shown to represent chromosome identity in several mammalian and lower eukaryotic organisms (Higashiyama et al 1997;Myler et al 1999;Kojima et al 2002;Sunkin et al 2002). In plant genomes, very little information on subtelomere sequence is available (Richards et al 1992) compared with the abundance of data obtained from numerous functional studies with telomeres and related proteins (Riha et al 2000(Riha et al , 2001Yu et al 2000;Chen et al 2001;Gallego and White 2001;Bundock and Hooykaas 2002;Riha and Shippen 2003). The two TATRs found on chromosomes 7 and 10 showed totally different and unique repeat sequences.…”

An N-terminal region of a Myb-like protein is involved in its intracellular localization and activation of a gibberellin-inducible proteinase gene in germinated rice seeds

“…28) Rice RTBP1 is categorized as type I and also binds telomeric DNA. 29) These characteristics indicate that the type I proteins are telomeric DNAbinding proteins. Conversely, type II proteins of A. thaliana cannot bind telomeric DNA.…”

“…1(B)). 27) A phylogenetic analysis of the sequences of the C-terminal Myb domain proteins of Arabidopsis thaliana, 28) rice (AK071645 and AK242392), 29,30) and Catharanthus roseus 25) revealed that this protein family is classified into 2 major groups: I and II (Supplemental Fig. 2).…”