Аннотация:Telomerase is a ribonucleoprotein; its main function is to synthe- size telomeres – repetitive sequences localized at the ends of eukaryotic chromosomes. Telomerase maintains stability of the genome in eukaryotic cells by replicating chromosomal ends. We identified several components of telomerase complex from H. polymorpha: catalytic subunit, the RNA telomerase component and additional proteins: Est1, Est3. We described structural features of the RNA telomerase component: template region, 3′ and 5′ ends, and elements of splicing, secondary structure. We show further that the H. polymorpha wild type telomerase synthesizes the product that contains the telomeric repeat in vitro plus an additional nontelomeric dT nucleotide that could not be detected in telomeres. We show that the incorporation of noncog- nate dT is the result of reverse transcription of the A170 nucleo- tide, which is located beyond the template in HpTER gene. The existence of additional nucleotides at the very end of the telomere that are not encoded by template of telomerase RNA was shown by deep sequencing of telomeres in case of strain with AC170CA HpTER gene. Mutational analysis of telomerase RNA confirmed that the incorporation of dT by telomerase in a nontelomeric position is functional and it is important for the telomere length control in H. polymorpha.