A plant gene encoding a Myb-like protein that binds telomeric GGTTTAG repeats in vitro

A gene (AtTRP1) encoding a telomeric repeat-binding protein has been isolat ed from Arabidopsis thaliana. AtTRP1 is a single copy gene located on chrom osome 5 of A. thaliana. The protein AtTRP1 encoded by this gene is not only homologous to the Myb DNA-binding motifs of other telomere-binding protein s but also is similar to several initiator-binding proteins in plants. Gel retardation assay revealed that the 115 residues on the C terminus of this protein, including the Myb motif, are sufficient for binding to the double- stranded plant telomeric sequence. The isolated DNA-binding domain of AtTRP 1 recognizes each telomeric repeat centered on the sequence GGTTTAG, The al most full-length protein of AtTRP1 does not form any complex at all with th e DNA fragments carrying four or fewer GGTTTAG repeats. However, it forms a complex with the sequence (GGTTTAG)(3) more efficiently than with the sequ ence (GGTTTAG)(5). These data suggest that the minimum length of a telomeri c DNA for AtTRP1 binding consists of five GGTTTAG repeats and that the opti mal AtTRP1 binding may require eight or more GGTTTAG repeats. it also impli es that this protein AtTRP1 may bind in vivo primarily to the ends of plant chromosomes, which consist of long stretches of telomeric repeats.