Component of the telomerase complex involved in telomere replication. Stimulates RNA/DNA heteroduplex unwinding which favors the telomere replication by the telomerase. Homodimer. Component of the telomerase complex composed of EST1, EST2, EST3 and the RNA component TLC1. Interacts with the telomerase RNA component TLC1 in presence of EST2. Produced by ribosomal frameshifting between codon Leu-92 and Val-93. Produced from conventional translation of the YIL009C-A ORF. There is no apparent role for isoform 2 in the cell. Belongs to the EST3 family.