In vitro Reconstitution of the Active T. castaneum Telomerase
Summary
Efforts to isolate the catalytic subunit of telomerase, TERT, in sufficient quantities for structural studies, have been met with limited success for more than a decade. Here, we present methods for the isolation of the recombinant Tribolium castaneum TERT (TcTERT) and the reconstitution of the active T. castaneum telomerase ribonucleoprotein (RNP) complex in vitro.
Abstract
Efforts to isolate the catalytic subunit of telomerase, TERT, in sufficient quantities for structural studies, have been met with limited success for more than a decade. Here, we present methods for the isolation of the recombinant Tribolium castaneum TERT (TcTERT) and the reconstitution of the active T. castaneum telomerase ribonucleoprotein (RNP) complex in vitro.
Telomerase is a specialized reverse transcriptase1 that adds short DNA repeats, called telomeres, to the 3′ end of linear chromosomes2 that serve to protect them from end-to-end fusion and degradation. Following DNA replication, a short segment is lost at the end of the chromosome3 and without telomerase, cells continue dividing until eventually reaching their Hayflick Limit4. Additionally, telomerase is dormant in most somatic cells5 in adults, but is active in cancer cells6 where it promotes cell immortality7.
The minimal telomerase enzyme consists of two core components: the protein subunit (TERT), which comprises the catalytic subunit of the enzyme and an integral RNA component (TER), which contains the template TERT uses to synthesize telomeres8,9. Prior to 2008, only structures for individual telomerase domains had been solved10,11. A major breakthrough in this field came from the determination of the crystal structure of the active12, catalytic subunit of T. castaneum telomerase, TcTERT1.
Here, we present methods for producing large quantities of the active, soluble TcTERT for structural and biochemical studies, and the reconstitution of the telomerase RNP complex in vitro for telomerase activity assays. An overview of the experimental methods used is shown in Figure 1.
Protocol
Discussion
The method presented here allows for the production of large amounts of the catalytic subunit of T. castaneum telomerase TERT in soluble, active form for structural and biochemical studies. The method of TcTERT over-expression is sensitive to subtle changes in temperature or cell density from those stated above and can dramatically affect the levels of protein expression. Specifically, we have found that inducing the cells for protein expression before the optical density reaches 0.5 at 600 nm, or lowe…
Disclosures
The authors have nothing to disclose.
Acknowledgements
The research presented here was supported by the Pennsylvania Department of Health, The Ellison Medical, The V and The Emerald Foundations.
Materials
| Name of Reagent | Company | Catalog Number |
|---|---|---|
| Rosetta(DE3)plysS Cells | Novagen | 70956 |
| 2YT Broth | Teknova | Y0215 |
| IPTG | Gold Biotechnology | I2481C |
| MISONIX Sonicator 3000 | Qsonica, LLC. | |
| ÄKTA Purifier FPLC | GE Life Sciences | |
| Ni-NTA Superflow Resin | Qiagen | 30410 |
| Amicon Ultra-15 Centrifugal Filter Device | Millipore | UFC903008 |
| POROS 50 HS Strong Cation Exchange Packing | Applied Biosystems | 1-3359-06 |
| POROS 50 HQ Strong Cation Exchange Packing | Applied Biosystems | 1-2559-06 |
| Superdex 200 10/300 Size-Exclusion Column | GE Life Sciences | 17-5175-01 |
| Phenol: Chloroform: Isoamyl 25:24:1 with 10mM Tris, pH 8, 1mM EDTA | Sigma | P3803-100mL |
| RNaseZap | Ambion | AM9780 |
| Recombinant Rnasin Ribonuclease Inhibitor | Promega | N251B |
| RNeasy Mini Kit | Qiagen | 74104 |
| DNA oligonucleotides | Integrated DNA Technologies |
References
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