Faculty Research Page
Professor of Biochemistry, Biophysics and Structural Biology*
*And Affiliate, Division of Cell and Developmental Biology
The eukaryotic ribonucleoprotein reverse transcriptase telomerase adds simple-sequence repeats to chromosome ends by copying a template within its RNA subunit. This new telomeric repeat synthesis balances the loss of repeats that occurs with each round of genome replication. We study telomerase both in vitro, to understand the structure and biochemical mechanisms of this unique polymerase, and in vivo, to understand the cellular regulation of telomerase-telomere interaction. Much of telomerase specialization has evolved through gained functions of motifs in the non-coding telomerase RNA. This insight led us to more general investigations of non-coding RNA and RNP biogenesis and function.
Many of our studies focus on the telomerase RNA and protein domains and protein-nucleic acid interactions that underlie the unique telomerase catalytic cycle of short repeat synthesis. Exploiting the ciliate Tetrahymena thermophila as a model system, we accomplished the affinity purification of an endogenously assembled telomerase holoenzyme. In parallel with ongoing studies of telomerase recruitment to telomeres in vivo, we have reconstituted the physiologically active telomerase holoenzyme from recombinant components. We are employing diverse approaches to characterize the dynamic interplay of protein, RNA, and DNA interactions, including collaborations for single molecule methods and high-resolution structure determination.
We are using biochemical, molecular, and cellular assays to investigate the function of human telomerase-associated proteins in comparison with their ciliate counterparts. One of the H/ACA proteins that we identified as a human telomerase holoenzyme protein was also identified as the product of the locus mutant in X-linked dyskeratosis congenita. We have shown that telomerase deficiency can completely account for the phenotypes of this human bone marrow failure syndrome and related syndromes of telomerase deficiency. We are continuing to tackle many remaining mysteries of human telomerase biogenesis and regulation in vivo, using cancer cell lines and now stem cells as well.
Tetrahymena RNA silencing pathways utilize Piwi proteins and several different classes of endogenous small RNAs to mediate gene and genome regulation. The most abundant small RNAs are generated by coupling between RNA-dependent RNA polymerase and Dicer in the cytoplasm. We have an interest in studying the principles governing the specificity of eukaryotic RNA-dependent RNA polymerase activity in vitro and in vivo. We are also exploring roles for nuclear-localized Piwi RNPs in RNA metabolism, gene control, and epigenetic inheritance.
Jiang J, Miracco EJ, Hong K, Eckert B, Chan H, Cash DD, Min B, Zhou ZH*, Collins K*, Feigon J* (*co-corresponding authors). The architecture of Tetrahymena telomerase holoenzyme. Nature 496: 187-192 (2013).
Katibah GE, Lee HJ, Huizar JP, Vogan JM, Alber T, Collins K. tRNA binding, structure, and localization of the human interferon-induced protein IFIT5. Mol. Cell 49: 743-750 (2013).
Couvillion MT, Bounova G, Purdom E, Speed TP, Collins K. A Tetrahymena Piwi bound to mature tRNA 3' fragments activates the exonuclease Xrn2 for RNA processing in the nucleus. Mol. Cell 48: 509-520 (2012).
Egan ED, Collins K. Biogenesis of telomerase ribonucleoproteins. RNA (2012).
Sexton AN, Youmans DT, Collins K. Specificity requirements for human telomere protein interaction with telomerase holoenzyme. J. Biol. Chem. (2012).
Egan ED, Collins K. An enhanced H/ACA RNP assembly mechanism for human telomerase RNA. Mol. Cell. Biol. 32: 2428-39 (2012).
Andersen KL, Collins K. Several RNase T2 enzymes function in induced tRNA and rRNA turnover in the ciliate Tetrahymena. Mol. Biol. Cell 23:36-44 (2012).
Zeng Z, Min B, Huang J, Hong K, Yang Y, Collins K, Lei M. Structural basis for Tetrahymena telomerase processivity factor Teb1 binding to single-stranded telomeric-repeat DNA. PNAS 108:20357-61 (2011).
Collins K. Single-stranded DNA repeat synthesis by telomerase. Curr. Op. Chem. Biol. 15:643-8 (2011).
Robart AR, Collins K. Human telomerase domain interactions capture DNA for TEN-domain-dependent processive elongation. Mol. Cell 42: 308-18 (2011).
Talsky KB, Collins, K. Initiation by a eukaryotic RNA-dependent RNA polymerase requires looping of the template end and is influenced by the template-tailing activity of an associated uridyltransferase. J. Biol. Chem. 285: 27614-27623 (2010).
Min B, Collins K. An RPA-related sequence-specific DNA binding subunit of telomerase holoenzyme is required for elongation processivity and telomere maintenance. Mol. Cell 36: 609-19 (2009).
Couvillion MT, Lee SR, Hogstad B, Malone CD, Tonkin LA, Sachidanandam R, Hannon GJ, Collins K. Sequence, biogenesis, and function of diverse small RNA classes bound to the Piwi-family proteins of Tetrahymena thermophila. Genes Dev. 23: 2016-32 (2009).
Photo credit: Mark Hanson of Mark Joseph Studios.
Last Updated 2013-06-03