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United States Biological
Newsletter

Telomerase:
telomeresTelomeres are specialized structures at the ends of eukaryotic chromosomes which appear to function in chromosome stabilization, positioning and replication. At each cell division, the length of telomeric TTAGGG DNA repeats is shortened and cells ultimately stop dividing. Telomerase is a reverse transcriptase that synthesizes telomere DNA thereby compensating for telomere loss. Telomerease is expressed mainly in the nucleus of proliferating cells and lymphocytes.

TERTIHC stainingIHC staining of TERT in lung

A sampling of Telomerase Antibodies:

anti-Telomerase, CT Rb x Hu
Immunogen: A synthetic peptide corresponding to residues in the C-terminus of human TERT. Suitable for use in Flow Cytometry, Western Blot, Immunohistochemistry and Immunocytochemistry.

anti-Telomerase Ch x Yeast
Immunogen: A 23aa peptide sequence mapping near the N-terminus of yeast telomerase/Est2. Suitable for use in ELISA and Western Blot.

anti-Telomerase Rb x Mo
Immunogen: Synthetic 15 amino acid peptide sequence mapping in the mid-region of mouse telomerase. Suitable for use in ELISA and Western Blot.

anti-Telomerase Rb x Hu
Immunogen: Recombinant protein corresponding to amino acids 174-341 of human telomerase. Suitable for use in Immunohistochemistry (paraffin-embedded sections).


Newsletter Special:
Select Teleomerase Control Peptides

T2395-10 Telomeric Repeat Binding Factor 1, Human (TRF1) (Control Peptide)
T2399-10 Telomerase, Mouse, Control Peptide (EST2, hEST2, TCS1, Telomerase Catalytic Subunit, Telomerase-associated protein 2, Telomere Reverse Transcriptase, TERT, TP2, TRT)
T2399-15 Telomerase, Human, Control Peptide (EST2, hEST2, TCS1, Telomerase Catalytic Subunit, Telomerase-associated protein 2, Telomere Reverse Transcriptase, TERT, TP2, TRT)
T2399-60 Telomerase, Human Control Peptide (EST2, hEST2, TCS1, Telomerase Catalytic Subunit, Telomerase-associated protein 2, Telomere Reverse Transcriptase, TERT, TP2, TRT)
T2399-65 Telomerase Protein, Mouse, Control Peptide (EST2, hEST2, TCS1, Telomerase Catalytic Subunit, Telomerase-associated protein 2, Telomere Reverse Transcriptase, TERT, TP2, TRT)
T2399-80 Telomerase, Control Peptide (EST2, hEST2, TCS1, Telomerase Catalytic Subunit, Telomerase-associated protein 2, Telomere Reverse Transcriptase, TERT, TP2, TRT)
T2400-10 Telomeric Repeat Binding Factor 2, Mouse (TRF2, RAP2) (Control Peptide)

This month's Special:
Selected Normal Adult Human First Strand cDNA

T5595-0025 Tissue, cDNA, First Strand, Human Adult Normal, Brain
T5595-0107
Tissue, cDNA, First Strand, Human Adult Normal, Heart
T5595-0143
Tissue, cDNA, First Strand, Human Adult Normal, Lung

c-DNA


2009 Nobel Prize in Medicine:
How  Chromosomes are Protected by Telomeres and Telomerase

The 2009 Nobel Prize in physiology or medicine is shared by Elizabeth H. Blackburn, Ph.D, of University of California, San Francisco; Carol W. Greider, Ph.D, of Johns Hopkins University School of Medicine; and Jack W. Szostak, Ph.D, of Massachusetts General Hospital, Harvard Medical School and Howard Hughes Medical Institute. The three researchers are honored for discovering how telomeres, through the enzyme telomerase, protect chromosomes against degradation.

Drs. Elizabeth Blackburn and Jack Szostak discovered that a unique DNA sequence in the telomeres protects chromosomes from degradation (1). Drs. Carol Greider and Elizabeth Blackburn further identified telomerase, the enzyme that makes telomere DNA (2,3). These discoveries explained how the ends of the chromosomes are protected by the telomeres and that they are extended by telomerase.

Telomeres are protein-DNA complexes that cap the ends of chromosomes, the structures that contain our DNA. Telomeres prevent chromosomes from unraveling and keep the ends of chromosomes from attaching to each other, which can contribute to cancer. Human telomeres consist of tandem repetitive arrays of the hexameric sequence TTAGGG, with overall telomere sizes ranging from 15 kb at birth to sometimes <5 kb in chronic disease states. These telomere repeats help maintain chromosomal integrity and provide a buffer of potentially expendable DNA.

Telomeres also act to limit the number of times a cell can divide. Before cells divide, they must copy all their DNA so the resulting cells have the same amount of genetic material. However, the genetic machinery of the cell can't copy the DNA all the way to the end tips, so telomeres gradually shorten with each cell division. When the telomeres become too short, the cell stops dividing or dies.

Telomerase, a reverse transcriptase enzyme, is responsible for elongating telomeres. It is usually not produced in normal adult cells, rather, it is expressed in cells such as embryonic cells, adult stem cells and immune cells, which are all responsible for producing other more specialized cells. In 80-90% of cancers, telomerase is reactivated—a hallmark of malignant cell transformation—enabling the cells to maintain long telomeres and divide indefinitely. This feature makes telomerase an attractive target for new cancer-fighting therapies. In addition, some inherited diseases are now known to be caused by telomerase defects, including certain forms of congenital aplastic anemia, and some inherited skin and lung diseases.

Telomerase is a ribonucleoprotein enzyme responsible for adding telomeric repeats onto the 3' ends of chromosomes. It has two major components (protein and RNA): an enzymatic human telomerase reverse transcriptase catalytic subunit, hTERT, and an RNA component (hTR or hTERC). Telomerase uses its integral RNA component as a template in order to synthesize telomeric DNA (TTAGGG)n, directly onto the ends of chromosomes. After adding six bases, the enzyme pauses while it repositions  the template RNA for the synthesis of the next 6 bp repeat.

During cell division, the ends of the chromosomes are not completely copied, so telomeres become progressively shorter. Over time telomeres become so short that their function is disrupted, and this, in turn, leads the cell to stop proliferating. Average telomere length, gives some indication of how many divisions the cell has already undergone and how many remain before it can no longer replicate.

In more recent work, Elissa Epel, Ph.D and Elizabeth Blackburn found evidence to support the long suspected association between stress and cellular aging. In this work, Epel and her colleagues demonstrated that both prolonged psychological stress and the perception of stress had a dramatic impact on three specific biological factors: oxidative stress, lower telomerase activity, and shorter telomere length -all of which are related to cell longevity and disease.

In comparing 39 healthy women caring for a chronically ill child with 19 healthy women raising a healthy child, Epel and her colleagues made the stunning discovery that the cells of the high stress women appeared to be about 13 years older, on average, than the cells of the low stress women (4). These findings have implications for understanding how, at the cellular level, stress may promote earlier onset of age-related diseases.

References:
1. Szostak, J.W., Blackburn, E.H. Cloning yeast telomeres on linear plasmid vectors. Cell (1982) 29:245-255.
2. Greider, C.W., Blackburn, E.H. Identification of a specific telomere terminal transferase activity in Tetrahymena extracts. Cell (1985) 43:405-413.
3. Greider, C.W., Blackburn, E.H. A telomeric sequence in the RNA of Tetrahymena telomerase required for telomere repeat
synthesis. Nature (1989) 337:331-337.
4. Epel, E.. et al, PNAS (2004) 101; 17312-17315.