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Telomerase can act as a template- and RNA-independent terminal transferase.

ABSTRACT: Telomerase is a special reverse transcriptase that extends one strand of the telomere repeat by using a template embedded in an RNA subunit. Like other polymerases, telomerase is believed to use a pair of divalent metal ions (coordinated by a triad of aspartic acid residues) for catalyzing nucleotide addition. Here we show that, in the presence of manganese, both yeast and human telomerase can switch to a template- and RNA-independent mode of DNA synthesis, acting in effect as a terminal transferase. Even as a terminal transferase, yeast telomerase retains a species-dependent preference for GT-rich, telomere-like DNA on the 5' end of the substrate. The terminal transferase activity of telomerase may account for some of the hitherto unexplained effects of telomerase overexpression on cell physiology.

SUBMITTER: Lue NF

PROVIDER: S-EPMC1174988 | biostudies-literature | 2005 Jul

REPOSITORIES: biostudies-literature

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Telomerase can act as a template- and RNA-independent terminal transferase.

Lue Neal F NF Bosoy Dimitry D Moriarty Tara J TJ Autexier Chantal C Altman Brian B Leng Siyang S

Proceedings of the National Academy of Sciences of the United States of America 20050630 28

Telomerase is a special reverse transcriptase that extends one strand of the telomere repeat by using a template embedded in an RNA subunit. Like other polymerases, telomerase is believed to use a pair of divalent metal ions (coordinated by a triad of aspartic acid residues) for catalyzing nucleotide addition. Here we show that, in the presence of manganese, both yeast and human telomerase can switch to a template- and RNA-independent mode of DNA synthesis, acting in effect as a terminal transfe ...[more]

PMID: 15994230

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Project description:Telomerase reverse transcriptase (TERT) and telomerase RNA (TR) represent the enzymatically active components of telomerase. In the complex, TR provides the template for the addition of telomeric repeats to telomeres, a protective structure at the end of linear chromosomes. Human TR with a mutation in the template region has been previously shown to inhibit proliferation of cancer cells in vitro. In this report, we examined the effects of a mutation in the template of a virus encoded TR (vTR) on herpesvirus-induced tumorigenesis in vivo. For this purpose, we used the oncogenic avian herpesvirus Marek's disease virus (MDV) as a natural virus-host model for lymphomagenesis. We generated recombinant MDV in which the vTR template sequence was mutated from AATCCCAATC to ATATATATAT (vAU5) by two-step Red-mediated mutagenesis. Recombinant viruses harboring the template mutation replicated with kinetics comparable to parental and revertant viruses in vitro. However, mutation of the vTR template sequence completely abrogated virus-induced tumor formation in vivo, although the virus was able to undergo low-level lytic replication. To confirm that the absence of tumors was dependent on the presence of mutant vTR in the telomerase complex, a second mutation was introduced in vAU5 that targeted the P6.1 stem loop, a conserved region essential for vTR-TERT interaction. Absence of vTR-AU5 from the telomerase complex restored virus-induced lymphoma formation. To test if the attenuated vAU5 could be used as an effective vaccine against MDV, we performed vaccination-challenge studies and determined that vaccination with vAU5 completely protected chickens from lethal challenge with highly virulent MDV. Taken together, our results demonstrate 1) that mutation of the vTR template sequence can completely abrogate virus-induced tumorigenesis, likely by the inhibition of cancer cell proliferation, and 2) that this strategy could be used to generate novel vaccine candidates against virus-induced lymphoma.

Dataset Information

Telomerase can act as a template- and RNA-independent terminal transferase.

Publications

Telomerase can act as a template- and RNA-independent terminal transferase.

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