IN-VITRO IDENTIFICATION OF A PROTEIN OF SACCHAROMYCES-CEREVISIAE THATINTERACTS SPECIFICALLY WITH THE G-RICH DNA STRAND OF THE TELOMERE

The telomeres of Saccharomyces cerevisiae consist of a repeated G(2-3) T(GT)(1-6) DNA sequence that forms a complex with proteins. To date on ly the RAP1 protein has been shown to bind to the simple sequences in yeast telomeric DNA, as well as to non-telemeric regulatory sites. We have used synthetic oligodeoxyribonucleotides, both double-and single- stranded, to identify specific yeast telomeric proteins in a partially purified yeast extract. Using the gel shift assay, we detected a bind ing activity that is stable at high ionic strength and that recognizes specifically the G-rich protrusion of a double-stranded synthetic yea st telomere, as well as the G-rich single strand. This is the first ev idence of a purely telomeric protein in that it binds to the single-st randed telomeric protrusion of the yeast chromosome.