INTRACELLULAR LOCALIZATION OF APOPTOTIC ENDONUCLEASE EndoG AND SPLICE VARIANTS OF TELOMERASE CATALYTIC SUBUNIT hTERT
The activity of telomerase catalytic subunit hTERT (human Telomerase Reverse Transcriptase) can be regulated by alternative splicing of its mRNA. The exact mechanism of hTERT splicing is not fully understood. Apoptotic endonuclease EndoG is known to participate in this process. The aim of this work was to investigate intracellular colocalization and mRNA levels of EndoG and splice variants of hTERT in normal and apoptotic cancer cells. We found that apoptosis development increased EndoG expression and changed the proportion of hTERT splice variants, which caused the downregulation of telomerase activity in cells. Apoptosis induction also caused a change in expression and localization of EndoG and of hTERT splice variants in cytoplasm, nuclei, and mitochondria of cells. EndoG silencing by small interfering RNA prevents induction of α+β- hTERT splice variant and inhibition of telomerase activity. We found a high level of intracellular colocalization of EndoG and hTERT. The changes in EndoG expression and localization corresponded with changes in hTERT mRNA levels and localization. Our data support the participation of EndoG in alternative splicing of mRNA of the telomerase catalytic subunit and regulation of telomerase activity.