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Science 30 January 2009:
Vol. 323. no. 5914, pp. 644 - 648
DOI: 10.1126/science.1165357
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Reports

A Human Telomerase Holoenzyme Protein Required for Cajal Body Localization and Telomere Synthesis

Andrew S. Venteicher,1,2 Eladio B. Abreu,3* Zhaojing Meng,4* Kelly E. McCann,1,5 Rebecca M. Terns,3 Timothy D. Veenstra,4 Michael P. Terns,3 Steven E. Artandi1,2,5{dagger}

Telomerase is a ribonucleoprotein (RNP) complex that synthesizes telomere repeats in tissue progenitor cells and cancer cells. Active human telomerase consists of at least three principal subunits, including the telomerase reverse transcriptase, the telomerase RNA (TERC), and dyskerin. Here, we identify a holoenzyme subunit, TCAB1 (telomerase Cajal body protein 1), that is notably enriched in Cajal bodies, nuclear sites of RNP processing that are important for telomerase function. TCAB1 associates with active telomerase enzyme, established telomerase components, and small Cajal body RNAs that are involved in modifying splicing RNAs. Depletion of TCAB1 by using RNA interference prevents TERC from associating with Cajal bodies, disrupts telomerase-telomere association, and abrogates telomere synthesis by telomerase. Thus, TCAB1 controls telomerase trafficking and is required for telomere synthesis in human cancer cells.

1 Department of Medicine, Stanford School of Medicine, Stanford, CA 94305, USA.
2 Program in Biophysics, Stanford School of Medicine, Stanford, CA 94305, USA.
3 Department of Biochemistry and Molecular Biology and Department of Genetics, University of Georgia, Athens, GA 30602, USA.
4 Laboratory of Proteomics and Analytical Technologies, Advanced Technology Program, Science Applications International Corporation (SAIC)–Frederick, National Cancer Institute (NCI)–Frederick, Frederick, MD 21702, USA.
5 Program in Cancer Biology, Stanford School of Medicine, Stanford, CA 94305, USA.

* These authors contributed equally to this work.

{dagger} To whom correspondence should be addressed. E-mail: sartandi{at}stanford.edu

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