THE CRYSTAL-STRUCTURE OF THE DNA-BINDING DOMAIN OF YEAST RAP1 IN COMPLEX WITH TELOMERIC DNA

Telomeres, the nucleoprotein complexes at the ends of eukaryotic chrom osomes, are essential for chromosome stability. In the yeast S. cerevi siae, telomeric DNA is bound in a sequence-specific manner by RAP1, a multifunctional protein also involved in transcriptional regulation. H ere we report the crystal structure of the DNA-binding domain of RAP1 in complex with a telomeric DNA site at 2.25 Angstrom resolution. The protein contains two similar domains that bind DNA in a tandem orienta tion, recognizing a tandemly repeated DNA sequence. The domains are st ructurally related to the homeodomain and the proto-oncogene Myb, but show novel features in their DNA-binding mode. A structured linker bet ween the domains and a long C-terminal tail contribute to the binding specificity. This structure provides insight into the recognition of t he conserved telomeric DNA sequences by a protein.