Carol Greider

On October 5, 2009, Carol Greider, Ph.D., one of the world’s pioneering researchers on the structure of chromosome ends known as telomeres, was awarded the 2009 Nobel Prize in Physiology or Medicine by the Royal Swedish Academy of Sciences. The Academy recognized her for her 1984 discovery of telomerase (ta-LAW-mer-ace), an enzyme that maintains the length and integrity of chromosome ends and is critical for the health and survival of all living cells and organisms.

Greider, is the Daniel Nathans Professor and Director of Molecular Biology and Genetics in the Johns Hopkins Institute for Basic Biomedical Sciences. This JScholarship collection showcases some of her ground-breaking research


Recent Submissions

Now showing 1 - 20 of 31
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    Short Telomeres Limit Tumor Progression In Vivo by Inducing Senescence
    (Cell Press, 2007-05) Greider, Carol W.; Feldser, David M.
    Telomere maintenance is critical for cancer progression. To examine mechanisms of tumor suppression induced by short telomeres, we crossed mice deficient for the RNA component of telomerase, mTR(-/-), with Emu-myc transgenic mice, an established model of Burkitt's lymphoma. Short telomeres suppressed tumor formation in Emu-myc transgenic animals. Expression of Bcl2 blocked apoptosis in tumor cells, but surprisingly, mice with short telomeres were still resistant to tumor formation. Staining for markers of cellular senescence showed that pretumor cells induced senescence in response to short telomeres. Loss of p53 abrogated the short telomere response. This study provides in vivo evidence for the existence of a p53-mediated senescence mechanism in response to short telomeres that suppresses tumorigenesis.
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    Identification of a Specific Telomere Terminal Transferase Activity in Tetrahymena Extracts
    (Cell Press, 1985-12) Blackburn, Elizabeth H.; Greider, Carol W.
    We have found a novel activity in Tetrahymena cell free extracts that adds tandem TTGGGG repeats onto synthetic telomere primers. The single-stranded DNA oligonucleotides (TTGGGG)4 and TGTGTGGGTGTGTGGGTGTGTGGG, consisting of the Tetrahymena and yeast telomeric sequences respectively, each functioned as primers for elongation, while (CCCCAA)4 and two nontelomeric sequence DNA oligomers did not. Efficient synthesis of the TTGGGG repeats depended only on addition of micromolar concentrations of oligomer primer, dGTP, and dTTP to the extract. The activity was sensitive to heat and proteinase K treatment. The repeat addition was independent of both endogenous Tetrahymena DNA and the endogenous alpha-type DNA polymerase; and a greater elongation activity was present during macronuclear development, when a large number of telomeres are formed and replicated, than during vegetative cell growth. We propose that the novel telomere terminal transferase is involved in the addition of telomeric repeats necessary for the replication of chromosome ends in eukaryotes.
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    The Telomere Terminal Transferase of Tetrahymena Is a Ribonucleoprotein Enzyme with Two Kinds of Primer Specificity
    (Cell Press, 1987-12-24) Blackburn, Elizabeth H.; Greider, Carol W.
    We have analyzed the de novo telomere synthesis catalyzed by the enzyme telomere terminal transferase (telomerase) from Tetrahymena. Oligonucleotides representing the G-rich strand of telomeric sequences from five different organisms specifically primed the addition of TTGGGG repeats in vitro, suggesting that primer recognition may involve a DNA structure unique to these oligonucleotides. The sequence at the 3' end of the oligonucleotide primer specified the first nucleotide added in the reaction. Furthermore, the telomerase was shown to be a ribonucleoprotein complex whose RNA and protein components were both essential for activity. After extensive purification of the enzyme by a series of five different chromatographic steps, a few small low abundance RNAs copurified with the activity.
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    Chromosome first aid
    (Cell Press, 1991-11-15) Greider, Carol W.
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    Purification of Tetrahymena Telomerase and Cloning of Genes Encoding the Two Protein Components of the Enzyme
    (Cell Press, 1995-06-02) Greider, Carol W.; Kobayashi, Ryuji; Collins, Kathleen
    Telomerase is a ribonucleoprotein DNA polymerase that catalyzes the de novo synthesis of telomeric simple sequence repeats. We describe the purification of telomerase and the cloning of cDNAs encoding two protein subunits from the ciliate Tetrahymena. Two proteins of 80 and 95 kDa copurified and coimmunoprecipitated with telomerase activity and the previously identified Tetrahymena telomerase RNA. The p95 subunit specifically cross-linked to a radiolabeled telomeric DNA primer, while the p80 subunit specifically bound to radiolabeled telomerase RNA. At the primary sequence level, the two telomerase proteins share only limited homologies with other polymerases and polymerase accessory factors.
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    Telomere Shortening and Tumor Formation by Mouse Cells Lacking Telomerase RNA
    (Cell Press, 1997-10-03) Greider, Carol W.; DePinho, Ronald A.; Lansdorp, Peter M.; Semper, Enrique; Hande, M. Prakash; Lee, Han-Woong; Blasco, Maria A.
    To examine the role of telomerase in normal and neoplastic growth, the telomerase RNA component (mTR) was deleted from the mouse germline. mTR-/- mice lacked detectable telomerase activity yet were viable for the six generations analyzed. Telomerase-deficient cells could be immortalized in culture, transformed by viral oncogenes, and generated tumors in nude mice following transformation. Telomeres were shown to shorten at a rate of 4.8+/-2.4 kb per mTR-/- generation. Cells from the fourth mTR-/- generation onward possessed chromosome ends lacking detectable telomere repeats, aneuploidy, and chromosomal abnormalities, including end-to-end fusions. These results indicate that telomerase is essential for telomere length maintenance but is not required for establishment of cell lines, oncogenic transformation, or tumor formation in mice.
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    Longevity, Stress Response, and Cancer in Aging Telomerase-Deficient Mice
    (Cell Press, 1999-03-05) DePinho, Ronald A.; Greider, Carol W.; Gottlieb, Geoffrey J.; Blasco, Maria; Lee, Han-Woong; Chang, Sandy; Rudolph, Karl Lenhard
    Telomere maintenance is thought to play a role in signaling cellular senescence; however, a link with organismal aging processes has not been established. The telomerase null mouse provides an opportunity to understand the effects associated with critical telomere shortening at the organismal level. We studied a variety of physiological processes in an aging cohort of mTR-/- mice. Loss of telomere function did not elicit a full spectrum of classical pathophysiological symptoms of aging. However, age-dependent telomere shortening and accompanying genetic instability were associated with shortened life span as well as a reduced capacity to respond to stresses such as wound healing and hematopoietic ablation. In addition, we found an increased incidence of spontaneous malignancies. These findings demonstrate a critical role for telomere length in the overall fitness, reserve, and well being of the aging organism.
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    Telomeres Do D-Loop–T-Loop
    (Cell Press, 1999-05-14) Greider, Carol W.
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    Short dysfunctional telomeres impair tumorigenesis in the INK4a(delta2/3) cancer-prone mouse.
    (Cell Press, 1999-05-14) DePinho, Ronald A.; Greider, Carol W.; Singer, Robert H.; Gottlieb, Geoffrey J.; Lee, Kee-Ho; Femino, Andrea; Chin, Lynda; Greenberg, Roger A.
    Maintenance of telomere length is predicted to be essential for bypass of senescence and crisis checkpoints in cancer cells. The impact of telomere dysfunction on tumorigenesis was assessed in successive generations of mice doubly null for the telomerase RNA (mTR) and the INK4a tumor suppressor genes. Significant reductions in tumor formation in vivo and oncogenic potential in vitro were observed in late generations of telomerase deficiency, coincident with severe telomere shortening and associated dysfunction. Reintroduction of mTR into cells significantly restored the oncogenic potential, indicating telomerase activation is a cooperating event in the malignant transformation of cells containing critically short telomeres. The results described here demonstrate that loss of telomere function in a cancer-prone mouse model possessing intact DNA damage responses impairs, but does not prevent, tumor formation.
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    p53 Deficiency Rescues the Adverse Effects of Telomere Loss and Cooperates with Telomere Dysfunction to Accelerate Carcinogenesis
    (Cell Press, 1999-05-14) DePinho, Ronald A.; Greider, Carol W.; Gottlieb, Geoffrey J.; Lee, Shwu-Luan; Tam, Alice; Shen, Qiong; Artandi, Steven E.; Chin, Lynda
    Maintenance of telomere length and function is critical for the efficient proliferation of eukaryotic cells. Here, we examine the interactions between telomere dysfunction and p53 in cells and organs of telomerase-deficient mice. Coincident with severe telomere shortening and associated genomic instability, p53 is activated, leading to growth arrest and/or apoptosis. Deletion of p53 significantly attenuated the adverse cellular and organismal effects of telomere dysfunction, but only during the earliest stages of genetic crisis. Correspondingly, the loss of telomere function and p53 deficiency cooperated to initiate the transformation process. Together, these studies establish a key role for p53 in the cellular response to telomere dysfunction in both normal and neoplastic cells, question the significance of crisis as a tumor suppressor mechanism, and identify a biologically relevant stage of advanced crisis, termed genetic catastrophe.
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    Secondary structure of vertebrate telomerase RNA
    (Cell Press, 2000-03-03) Greider, Carol W.; Blasco, Maria A.; Chen, Jiunn-Liang
    Telomerase is a ribonucleoprotein enzyme that maintains telomere length by adding telomeric sequence repeats onto chromosome ends. The essential RNA component of telomerase provides the template for telomeric repeat synthesis. To determine the secondary structure of vertebrate telomerase RNA, 32 new telomerase RNA genes were cloned and sequenced from a variety of vertebrate species including 18 mammals, 2 birds, 1 reptile, 7 amphibians, and 4 fishes. Using phylogenetic comparative analysis, we propose a secondary structure that contains four structural domains conserved in all vertebrates. Ten helical regions of the RNA are universally conserved while other regions vary significantly in length and sequence between different classes of vertebrates. The proposed vertebrate telomerase RNA structure displays a strikingly similar topology to the previously determined ciliate telomerase RNA structure, implying an evolutionary conservation of the global architecture of telomerase RNA.
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    Telomere Dysfunction Increases Mutation Rate and Genomic Instability
    (Cell Press, 2001-08-10) Greider, Carol W.; Feldser, David M.; Hackett, Jennifer A.
    The increased tumor incidence in telomerase null mice suggests that telomere dysfunction induces genetic instability. To test this directly, we examined mutation rate in the absence of telomerase in S. cerevisiae. The mutation rate in the CAN1 gene increased 10- to 100- fold in est1􏰋 strains as telomeres became dysfunc- tional. This increased mutation rate resulted from an increased frequency of terminal deletions. Chromo- some fusions were recovered from est1􏰋 strains, sug- gesting that the terminal deletions may occur by a breakage-fusion-bridge type mechanism. At one lo- cus, chromosomes with terminal deletions gained a new telomere through a Rad52p-dependent, Rad51p- independent process consistent with break-induced replication. At a second locus, more complicated re- arrangements involving multiple chromosomes were seen. These data suggest that telomerase can inhibit chromosomal instability.
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    The Shortest Telomere, Not Average Telomere Length, Is Critical for Cell Viability and Chromosome Stability
    (Cell Press, 2001-10-05) Greider, Carol W.; Hao, Ling-Yang; Strong, Margaret A.; Hemann, Michael T.
    Loss of telomere function can induce cell cycle arrest and apoptosis. To investigate the processes that trig- ger cellular responses to telomere dysfunction, we crossed mTR􏰀/􏰀 G6 mice that have short telomeres with mice heterozygous for telomerase (mTR􏰁/􏰀) that have long telomeres. The phenotype of the telomerase null offspring was similar to that of the late generation parent, although only half of the chromosomes were short. Strikingly, spectral karyotyping (SKY) analysis revealed that loss of telomere function occurred pref- erentially on chromosomes with critically short telo- meres. Our data indicate that, while average telomere length is measured in most studies, it is not the aver- age but rather the shortest telomeres that constitute telomere dysfunction and limit cellular survival in the absence of telomerase.
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    Tracking Telomerase
    (2004-01-23) Blackburn, Elizabeth H.; Greider, Carol W.
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    Short Telomeres, even in the Presence of Telomerase, Limit Tissue Renewal Capacity
    (Cell Press, 2005-12-16) Greider, Carol W.; Huso, David; Feldser, David M.; Karim, Baktiar; Strong, Margaret A.; Armanios, Mary; Hao, Ling-Yang
    Autosomal-dominant dyskeratosis congenita is associated with heterozygous mutations in telomerase. To examine the dosage effect of telomerase, we generated a line of mTR+/ÿ mice on the CAST/EiJ background, which has short telomeres. Interbreeding of heterozygotes resulted in progressive telomere shortening, indicating that limiting telomerase compromises telomere mainte- nance. In later-generation heterozygotes, we observed a decrease in tissue renewal capacity in the bone marrow, intestines, and testes that resembled defects seen in dyskeratosis congenita patients. The pro- gressive worsening of disease with decreasing telomere length suggests that short telo- meres, not telomerase level, cause stem cell failure. Further, wild-type mice derived from the late-generation heterozygous parents, termed wt*, also had short telomeres and displayed a germ cell defect, indicating that telomere length determines these phenotypes. We propose that short telomeres in mice that have normal telomerase levels can cause an occult form of genetic disease.
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    Functional reconstitution of wild-type and mutant Tetrahymena telomerase
    (Cold Spring Harbor Laboratory Press, 1994-03-01) Greider, Carol W.; Autexier, Chantal
    Telomerase is a ribonucleoprotein that catalyzes telomere elongation in vitro and in vivo. The 159-nucleotide RNA component of Tetrahymena telomerase contains the sequence 5'-CAACCCCAA-3' ("template region"), which serves as a template for the addition of the sequence d(TTGGGG)n to Tetrahymena telomeres. To dissect the Tetrahymena telomerase enzyme mechanism, we developed a functional in vitro reconstitution assay. After removal of the essential telomerase RNA by micrococcal nuclease digestion of partially purified telomerase, the addition of in vitro-transcribed telomerase RNA reconstituted telomerase activity. The reconstituted activity was processive and showed the same primer specificities as native telomerase. Mutants in the RNA template region were tested in reconstitution assays to determine the role of the residues in this region in primer recognition and elongation. Two template mutants, encoding the sequences 5'-UAACCCCAA-3' and 5'-UAACCCUAA-3', specified the incorporation of dATP into the sequence d(TTAGGG). Telomerase reconstituted with a template mutant encoding the sequence 5'-CAACCCUAA-3' did not specify dATP incorporation and elongation by this mutant was not terminated by the addition of ddATP. In addition, a template mutant encoding the sequence 5'-CGGCCCCAA-3' specified the incorporation of ddCTP but not ddTTP while a mutant encoding the sequence 5'-CAACCCCGG-3' specified the incorporation of ddTTP but not ddCTP. These data suggest that only the most 5' six residues of the template region dictate the addition of telomeric repeats.
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    The RNA component of human telomerase
    (American Association for the Advancement of Science, 1995-09-01) Greider, Carol W.; Feng, Junli
    Eukaryotic chromosomes are capped with repetitive telomere sequences that protect the ends from damage and rearrangements. Telomere repeats are synthesized by telomerase, a ribonucleic acid (RNA)-protein complex. Here, the cloning of the RNA component of human telomerase, termed hTR, is described. The template region of hTR encompasses 11 nucleotides (5'-CUAACCCUAAC) complementary to the human telomere sequence (TTAGGG)n. Germline tissues and tumor cell lines expressed more hTR than normal somatic cells and tissues, which have no detectable telomerase activity. Human cell lines that expressed hTR mutated in the template region generated the predicted mutant telomerase activity. HeLa cells transfected with an antisense hTR lost telomeric DNA and began to die after 23 to 26 doublings. Thus, human telomerase is a critical enzyme for the long-term proliferation of immortal tumor cells.
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    Functional characterization and developmental regulation of mouse telomerase RNA
    (American Association for the Advancement of Science, 1995-09-01) Greider, Carol W.; Villeponteau, Bryant; Funk, Walter; Blasco, Maria A.
    Telomerase synthesizes telomeric DNA repeats onto chromosome ends de novo. The mouse telomerase RNA component was cloned and contained only 65 percent sequence identity with the human telomerase RNA. Alteration of the template region in vivo generated altered telomerase products. The shorter template regions of the mouse and other rodent telomerase RNAs could account for the shorter distribution of products (processivity) generated by the mouse enzyme relative to the human telomerase. Amounts of telomerase RNA increased in immortal cells derived from primary mouse fibroblasts. RNA was detected in all newborn mouse tissues tested but was decreased during postnatal development.
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    A critical stem-loop structure in the CR4-CR5 domain of mammalian telomerase RNA
    (Oxford University Press, 2002-01-15) Greider, Carol W.; Opperman, Kay Keyer; Chen, Jiunn-Liang
    Telomerase is an enzyme that maintains telomere length by adding telomeric sequence repeats onto chromosome ends. The telomerase ribonucleoprotein complex consists of two essential components, a reverse transcriptase and an RNA molecule that provides the template for telomeric repeat synthesis. A common secondary structure of vertebrate telomerase RNA has been proposed based on a phylogenetic comparative analysis of 35 sequences. Here we report the identification of an additional essential base-paired region in the CR4-CR5 domain of mammalian telomerase RNA, termed P6.1. Mouse telomerase RNAs with mutations that disrupted base pairings in the P6.1 helix were unable to reconstitute telomerase activity in vivo. In contrast, an RNA mutant with compensatory mutations that restored base pairings in the P6.1 helix restored telomerase activity. In an in vitro reconstitution system stable base pairing of the P6.1 stem was required for the RNA-protein interaction between the CR4-CR5 domain and the telomerase reverse transcriptase (TERT) protein. Interestingly, two RNA mutations, one that extends the P6.1 stem and one that alters the conserved nucleotides of the L6.1 loop, allowed RNA-protein binding but significantly impaired telomerase activity. These data establish the presence of the P6.1 stem-loop and its importance for the assembly and enzymatic activity of the mammalian telomerase complex.
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    Wild-derived inbred mouse strains have short telomeres
    (Oxford University Press, 2000-11-15) Greider, Carol W.; Hemann, Michael T.
    Telomere length and telomerase activity directly affect the replicative capacity of primary human cells. Some have suggested that telomere length influences organismal lifespan. We compared telomere length distributions in a number of inbred and outbred established mouse strains with those of strains recently derived from wild mice. Telomere length was considerably shorter in wild-derived strains than in the established strains. We found no correlation of telomere length with lifespan, even among closely related inbred mouse strains. Thus, while telomere length plays a role in cellular lifespan in cultured human cells, it is not a major factor in determining organismal lifespan.