BOUNDARY ELEMENTS OF THE TETRAHYMENA TELOMERASE RNA TEMPLATE AND ALIGNMENT DOMAINS

Telomerase is a DNA polymerase fundamental to the replication and main tenance of telomere sequences at chromosome ends. The RNA component of telomerase is essential for the synthesis of telomere repeats. In vit ro, the template domain (5'-CAACCCCAA-3') of the Tetrahymena telomeras e RNA dictates the addition of Tetrahymena-specific telomere repeats d (TTGGGG)(n), onto the 3' end of G-rich or telomeric substrates that ar e base-paired with the template and alignment regions of the RNA. Usin g a reconstituted in vitro system, we determined that altering the seq uence of the alignment and template domains affects processivity of te lomerase without abolishing telomerase activity. These results suggest that alternative template/alignment regions may be functional. In the ciliate telomerase RNAs, there is a conserved sequence 5'-(CU)GUCA-3' , located two residues upstream of the template domain. The location a nd sequence of this conserved domain defined the 5' boundary of the te mplate region. These data provide insights into the regulation of telo mere synthesis by telomerase.