Figure 1. Structure of shuttle vector containing telomeric DNA. Six telomeric repeats were inserted upstream and within the supF gene of the pSP189 shuttle vector as shown. Four nucleotides of the supF gene were mutated as indicated so the last repeat was located in the stem of the supF tRNA hairpin structure. A scrambled telomeric sequence of identical size and nucleotide context was introduced to generate the control shuttle vector (see Table S1). The chloramphenicol aceytltransferase gene was introduced at the BamHI site. The 5' end of the mature tRNA (*G) is marked as position 99 following the traditional nomenclature.