ИСТИНА

Telomeres are special regions of repetitive nucleotide sequences at the ends of chromosomes. The number of these repeats determines the maximal number of cell divisions before its programmable death. Telomerase is a unique enzyme, which is capable of synthesizing telomeric DNA, templated by its own RNA subunit. Normally telomerase is active in embryonic and stem cells giving them potential for unlimited divisions. Telomerase is inactive in somatic cells. Telomerase activation in somatic cells is strongly correlated with cancer development. It is active in 90% of all tumor types. Our laboratory research is devoted to the problem of biogenesis of telomerase RNA (TER) in thermotolerant yeast species Hansenula polymorpha. The aim of the work is to determine the mechanism of telomerase RNA processing. Common pathway of yeast telomerase RNA maturation is associated with Sm-protein complex. Sm-complex binds a special RNA region called Sm-site, thus protecting telomerase RNA from degradation via nucleases. Telomerase RNA of Hansenula polymorpha (HpTER) lacks canonical Sm-site. This suggests the existence of an alternative mechanism. We created two new H. polymorpha strains, which express tagged proteins Smb1 and Lsm4, which are supposed to be the participants of classical Sm-dependent mechanism. Affinity chromatography followed by qRT-PCR showed that Smb1 and Lsm4 proteins do not bind HpTER. These data allowed us to develop the theory of the unique Sm-independent HpTER processing mechanism. To determine an alternative biogenesis pathway the following approach has been developed. Two model structures imitating the 3’-end of HpTER and additionally containing biotin or pp7-hairpin for affinity chromatography have been synthesized. Using these structures we try to find new proteins involved in the process of HpTER maturation