Contents 1 Pinyin 2 Definition of telomerase 3 Application of telomerase 4 Telomere DNA function and telomerase function and biological properties 5 Aging mechanism and telomerase issues 5.1 About the molecular mechanism of cellular aging Mainstream hypothesis 5.2 Telomeres and anti-aging 5.3 The story of searching for the aging clock 5.4 The hopeful road to anti-aging 6 Nobel Prize 7 Test 7.1 Normal value 7.2 The significance of test results 7.3 Test materials 7.4 Test method 7.5 Test category 7.6 Reference 1 Pinyin
duān lì méi 2 Definition of telomerase
Telomerase is a basic nucleoprotein reverse transcriptase that can add telomeric DNA to the ends of eukaryotic chromosomes. . Telomeres play an important role in maintaining chromosome stability and cell activity in cells of different species. Telomerase can lengthen shortened telomeres (shortened telomeres have limited cell replication ability), thereby enhancing the proliferation ability of cells in vitro. The activity of telomerase is inhibited in normal human tissues and reactivated in tumors. Telomerase may be involved in malignant transformation. Telomerase plays an important role in maintaining telomere stability, genome integrity, long-term cell activity and potential continued proliferation.
There is an enzyme in cells responsible for the extension of telomeres, called telomerase. The existence of telomerase can be regarded as filling the defects of the DNA cloning mechanism. By prolonging the repair of telomeres, telomeres can be prevented from being lost due to cell division, increasing the number of cell divisions and cloning.
However, in normal human cells, the activity of telomerase is quite tightly regulated, only in hematopoietic cells, stem cells and germ cells, which must continue to divide and clone cells. Among them, active telomerase can be detected. When cells differentiate and mature, they must be responsible for the needs of various tissues in the body and perform their respective duties. Therefore, the activity of telomerase will gradually disappear. It does not matter whether the cells themselves can continue to divide and clone. Instead, differentiated and mature cells will shoulder a more important mission, which is to allow tissues and organs to function and to continue life, but it is not sustainable. This cycle of alternation of generations is the creator's ingenuity in the design of life. 3 Application of Telomerase
It is generally believed that the reactivation of telomerase activity can maintain the length of telomeres, and delaying cells from entering clonal aging is a key step for cells to become immortal. Restoring telomerase activity in epidermal fibroblasts indeed extends the lifespan of cell division, allowing the cells to remain young for longer periods of time.
In addition, in medical applications, take the endothelial cells of blood vessels as an example. The endothelial cells of blood vessels are damaged very quickly under the constant erosion of blood flow. When an individual is young, the surrounding tissues can continuously provide new cells. To repair damage to the blood vessel wall, once an individual ages, new cells cannot be provided around the damage to repair, and the arteries will gradually develop symptoms of hardening. If the telomerase of cells in the surrounding tissue is activated, the telomeres are lengthened and the number of cell divisions increases, causing the surrounding tissue to continuously provide new cells to fill the damage to the blood vessels, thus delaying the signs of aging caused by vascular sclerosis. Just like the basic theory behind the search for telomerase inhibitors, scientists are actively using the same strategy to also search for activators of telomerase.
Overall, the mechanisms of aging and cancer are more complex than we imagined. Since they are diseases caused by multiple factors, prevention and treatment in one direction are not enough to cover all causes. The study of telomerase and telomerase is only part of the exploration of aging mechanisms.
Telomerase allows humans to see the dawn of immortality 4 Telomere DNA functions and telomerase functions and biological properties
Telomeres are the ends of chromosomes in eukaryotic cells. Special structure. Human telomeres are composed of 6 base repeat sequences (TTAGGG) and binding proteins. Telomeres have important biological functions, which can stabilize the function of chromosomes, prevent chromosomal DNA degradation and terminal fusion, protect chromosome structural genes, and regulate normal cell growth. In normal cells, due to the disappearance of the 5' end of linear DNA replication, telomeres gradually shorten as somatic cells continue to proliferate. When the cell telomeres shrink to a certain extent, the cells stop dividing and are in a quiescent state. Therefore, some people call telomeres the "division of normal cells" "Mistosis clock" (Mistosis clock), telomere length and stability determine cell lifespan and are closely related to cell aging and canceration. Telomerase is a reverse transcription DNA synthase that extends telomeres. It is a ribonucleic acid protein complex composed of RNA and protein. The RNA component serves as a template, the protein component has catalytic activity, and the 3' end of the telomere is used as a primer to synthesize telomeric repeat sequences. The activity of telomerase can be detected in eukaryotic cells. Its function is to synthesize telomeres at the ends of chromosomes to compensate for the gradually shortened telomere length due to each cell division, thereby stabilizing telomere length. The main feature is to use the RNA it carries as a template to synthesize DNA through reverse transcription.
The main biological function of telomerase in cells is to replicate and extend telomere DNA through its reverse transcriptase activity to stabilize the length of telomere DNA. Research on the relationship between telomerase and tumors in recent years Progress shows that telomerase is also involved in the regulation of apoptosis and genome stability in tumor cells. Corresponding to the multiple biological activities of telomerase, there is also a complex telomerase regulatory network in tumor cells. .Regulation of telomerase activity and function at the post-translational level through protein-protein interactions is one of the current hot spots in research on the regulatory mechanism of telomerase.
Telomeres exist to maintain chromosomes. Stable. Without telomeres, the ends are exposed and easily hydrolyzed by exonucleases.
Telomeres are not synthesized by DNA polymerase, but by telomerase. Telomerase contains RNA templates and is used to synthesize telomeres. 5 Aging mechanism and telomerase issues
The aging mechanism (link) The first question that must be clarified is why people die. Only with a thorough understanding of the mechanism of this process, immortality is not impossible.
Regarding the mechanisms of human aging and death, I know of several mechanisms. For example, an imbalance in the free radical scavenging and production mechanisms in the body leads to the accumulation of harmful free radicals over time, which in turn damages cell organelles. Mitochondria have been confirmed to be involved in this. A process.
The telomerase you proposed is also one of the explanations. Since normal human cells do not have telomerase, they cannot repair the DNA shortening problem caused by DNA replication. Therefore, as the number of cell replications increases and the DNA becomes shorter to a certain extent, the death mechanism may be triggered, or death may be an asymptotic process. process. 5.1 Mainstream hypotheses on the molecular mechanism of cell senescence
1. Oxidative damage. From the accumulation of free radicals.
2. rDNA. During chromosome replication, mismatches may occur and bulging extrachromosomal rDNA circles, called ERCs, may occur. Its accumulation leads to cellular senescence, accompanied by nucleolar lysis.
3. Silent information regulatory protein complex. It blocks DNA transcription at its site.
4. SGS1 gene and WRN gene. These are two homologous genes that are necessary to ensure the normal life cycle of cells, but they are prone to mutations leading to progeria.
5. Developmental program.
6. Mitochondrial DNA. Over time, mutations in mitochondrial DNA are quite significant.
Life is the most amazing magic.
The actions in cells are complex and precise. It is often foreign drugs that cause protein phosphorylation, which is transmitted level by level, activates certain genes, and begins to transcribe and translate proteins that do not usually exist. This protein then causes the next step. Series cascade reaction. To overturn the laws of nature and solve an enzyme problem is nothing more than a drop in the bucket.
But even assuming that the human body has telomerase, longevity is still a question worth putting a question mark on. Because telomerase only solves the problem of replication length, it cannot solve the problem of mutation during DNA replication. Of course, there are specialized agencies responsible for this. But this also shows that immortality is not as simple as imagined, and more than just telomerase can solve it. 5.2 Telomeres and anti-aging
What are telomeres?
A telomere is a segment of DNA at the end of a chromosome.
The DNA arranged on the lines determines the characteristics of the human body. They determine the straightness or curliness of the person's hair, the blueness or blackness of the eyes, the height or shortness of the person, etc., and even the violent or gentle personality.
In fact, telomeres are also DNA, but telomeres are repeated DNA at the head and tail of chromosomes. I think of telomeres as a piece of woolen sweater, the thread segments that fall off the cuffs, and the woolen sweater is like a tightly structured DNA. Cytologists have never been interested in the DNA dragged out by the tails of chromosome rods. They focused on the 46 stained genetic maps and made a lot of noise about the draft human genome.
Since 1990, Calvin Harley has linked telomeres to human aging. He made three points, which I recorded as follows: First, the older the cell, the shorter the telomere length; the younger the cell, the longer the telomere, and telomeres are related to cell aging.
Some telomeres in senescent cells have lost large portions of their telomeric repeats. When the function of cell telomeres is damaged, aging occurs. When telomeres shorten to a critical length, aging is accelerated and death approaches.
Second, normal cells have shorter telomeres. Cell division will shorten the telomeres. Once they divide, they shorten a little, just like wearing out an iron rod. If only a stub is left, the cell is close to senescence. Once a cell divides, its telomere DNA loses about 30,200 bp (base pairs), and some cells in mice and humans generally have about 10,000 bp.
Third, research has found that there is an enzyme in cells that synthesizes telomeres. The length of telomeres is determined by enzymes. More enzymes and less enzymes in cells can predict the length of telomeres. Telomerase is not detectable in normal human cells. Some benign disease cells and fibroblasts cultured in vitro also have no detectable telomerase activity. However, this enzyme is positive in germ cells testis, ovary, placenta and fetal cells. The striking discovery is that malignant tumor cells have highly active telomerase. Telomerase-positive tumors include ovarian cancer, lymphoma, acute leukemia, breast cancer, colon cancer, lung cancer, etc. High telomerase activity is widely found in human tumors. In this way, we discovered another substance specific to tumor cells. 5.3 The story of searching for the aging clock
The human body is composed of cells. As people age, do cells also age? It's like a building, its longevity has a lot to do with the bricks that make it up. Cells have a lifespan. This was discovered by the cytologist Hayflick forty years ago. He cultivated human fibroblasts from generation to generation. However, when nutrients are fully supplied, cell division ceases around the 50s and truly enters the aging period. This discovery seems to tell people that there is an aging clock in cells, which limits the number of cell divisions, that is, Limits the lifespan of living things. Because longevity organisms are formed by the division of a fertilized egg cell, which divides into two, and then divides into four, and so on, it multiplies to form a fetus, and then divides to form a young man. If cells can no longer divide, the individual will age. 5.4 A promising road to anti-aging
To this day, I dare not say that scientists have pinpointed the real cause of aging. However, the discovery of telomere function has indeed opened up a new anti-aging path for us. The road to decline.
Telomere shortening causes aging. If telomere length is not maintained, cells stop dividing or die. Under certain circumstances, dying cells become immortal cells, that is, cancer cells.
The discovery of telomerase provides a logical explanation for the millennium-troubling problems of normal cells, aging and cancer. Simply put, it is possible to inject telomerase into aging cells to extend the length of telomeres and rejuvenate the cells, and scientists have high hopes for this. In the future, doctors will inject preparations similar to telomerase into the elderly to extend the length of their telomeres and achieve the purpose of rejuvenation.
Some scholars have proposed that telomerase inhibitors can be used as drugs to treat cancer. Because telomerase is only found in cancer cells, if the enzyme is depleted, the cancer cells appear to stop multiplying. Of course, there are many difficulties that need to be overcome.
As early as the 1930s, geneticist Mullert discovered that the structure of chromosome ends is very important for maintaining chromosome stability, and named it (telonereTLM). In 1978, Blackburn and Gall first discovered and confirmed it in Tetrahymena The structure of telomeres. Telomeres are composed of telomeric DNA and telomeric proteins. They found that the end of each chain of this rDNA contained a large number of repeating segments. Later, they found that the vast majority of eukaryotic DNA ends are composed of a large number of repeats of a specific basic sequence unit, the telomere sequence. For a given Eukaryotic species must have characteristic telomeric DNA sequences.
Telomeres are a special structure at the ends of chromosomes. They are composed of many simple short repeat sequences and telomere binding proteins (telomere end binding protein (TEBP). In normal human cells, it can gradually shorten as cells divide. Telomeres are an essential genetic component of cells because they can protect and compensate for the loss of genetic information at the ends of chromosomes, protecting them from being Recognized by nucleases and protected from degradation. However, during the replication process, telomeres are also slowly lost due to lack of replication mechanisms or other reasons. In new cells, every time the cell divides, the telomeres at the top of the chromosomes are shortened (cell The DNA of the telomere is lost (approximately 30 to 200 bp after one division). When the telomeres can no longer be shortened, the cell cannot continue to divide. Further studies have shown that some telomeres in senescent cells have lost most of the telomeric repeat sequences. Kevin in 1990. Calvin Harley discovered that the lifespan of somatic cells in people of different ages is significantly different, and the length of their telomeres is also different. It shortens with age. The older the cell, the shorter the telomere length; the younger the cell, the longer the telomere. Telomeres are related to cell aging, so telomeres are used to explain the new human aging mechanism. In addition, the loss of telomeres is also related to many causes. Maria Blasco and Piero Anversa's research explored the impact of telomere dysfunction in some cardiovascular pathological conditions. Maria Blasco and Piero Anversa constructed a second-generation G2 and third-generation 5th generation G5 telomeric RNA-deleted transgenic mice (Terc/). The researchers performed in situ quantitative fluorescence hybridization analysis on cardiomyocytes from G5 (Terc/) mice and found that these cells had shorter telomeres than G2 (Terc/) mice. The telomeres of G2 (Terc/) mouse cardiomyocytes Telomeres are also shorter than those of wild-type cells. In the "Journal of the European Molecular Biology Organization" on March 15, 1996, Dr. Shay and Dr. Wright [6] from UT Southwestern Medical Center in Dallas reported the results of research on changing the lifespan of human cells by controlling telomere length. They found that by increasing the length of telomeres, the lifespan of the cell hybrid lines could be extended.
However, it should be mentioned that whether the reduction of telomeres leads to atherosclerosis needs further study.
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Research has found that there is an enzyme in cells that synthesizes telomeres. The replication of telomeres cannot be catalyzed by classic DNA polymerase, but is completed by a special reverse transcriptase, telomerase.
Telomerase is an enzyme that synthesizes DNA using RNA as a template. Telomerase is a ribonucleoprotein composed of RNA and protein. Its RNA component is the template for telomeric sequence synthesis. Telomerases from different organisms have different RNA templates and synthesize telomere sequences that are also different. Mutagenesis of telomerase RNA; new telomere sequences corresponding to the mutated RNA sequences can be synthesized in vivo, proving the template function of RNA. Telomerase synthesizes the telomere DNA fragment TTAGGG, and its gene is located on human chromosome 3q.26.3. Telomerase is not detectable in normal human cells. Some benign disease cells and fibroblasts cultured in vitro also have no detectable telomerase activity. However, this enzyme is positive in germ cells, testicles, ovaries, placenta and fetal cells. Research shows that this is why scientists have begun to study how telomeres in cancer cells and cancer cells are not shortened for a long time.
It is worth noting that malignant tumor cells have highly active telomerase (it can maintain the length of cancer cell telomeres and allow them to expand without restriction. Regarding how cancer cells obtain immortality, Ha in 1991 rley proposed the telomerase hypothesis. It is believed that normal cell death goes through two stages: the first Mortality Stage 1 (Mortality Stage 1) and the second stage M2 (Mortality Stage 2). That is, telomere DNA is continuously lost during the process of cell mitosis. The telomeres are shortened. When the telomeres are shortened to a certain length (2kb~4kb), the stability of the chromosomes is destroyed, the cells appear to be senescent, and the cells enter the first death phase, M1 phase. At this time, the cells no longer divide, but. It exits the cell cycle and ages and dies. If the cells have been infected by viruses (SV40, HPV), oncogenes are activated or tumor suppressor genes (P53, Rb) are inactivated, the cells can cross the M1 phase and continue to divide 2030 times. , telomeres continue to shorten, and eventually enter the second lethal phase, M2, where most cells lose function and die due to too short telomeres. Only a few cells have telomerase activated to repair and maintain the length of telomeres. , allowing cells to escape the M2 phase and obtain immortality.) This is also a hot research topic in the field of contemporary scientific research. In 1995, Hiyama et al. [8] confirmed in a study of 100 cases of fibroblastoma that there was telomerase activity 94% of the tumor tissues express it. Tissues with higher telomerase activity are more likely to be accompanied by other genetic changes and have a poor prognosis; while no corresponding changes are found in tumor tissues with low telomerase activity and all have a good prognosis, even Three cases in the IVS stage without telomerase activity actually experienced tumor regression. This seems to indicate that there is a correlation between telomerase and cancer, but it is difficult to determine whether there is a causal relationship.
Telomere DNA includes non-specific DNA and specific DNA sequences composed of highly repetitive sequences. It is usually composed of short tandem repeats rich in guanine nucleotides (G), extending to the 3' end of the chromosome. Artificially synthesized Tetrahymena telomeric repetitive DNA fragments (TTGGGG) 4. Human and mouse The telomeric DNA sequence is TTGGG. The length of human telomeres is approximately 15Kb. Due to the end replication problem of dsDNA, every time a cell divides, it loses about one DNA segment length, that is, 25 to 100 pairs of bases. Telomerase adds the DNA repeat sequence synthesized by its own RNA template to the subsequent linkage link. 3' end, and then use the extended parent strand as a template to synthesize the daughter strand by DNA polymerase. However, due to the incompleteness of the replication mechanism (or is this incompleteness retained by evolution? This mechanism ensures the regularity of cells Aging and death?). Telomeres are still lost at a certain rate. Telomerase is a nuclear protein (RNP) mainly composed of RNA and protein. Telomerase is a special DNA polymerase necessary for telomere replication. Currently, the telomerase RNA of many organisms has been cloned, but the nucleotide sequences of different species vary greatly. The telomerase RNA template of Tetrahymena is 160 to 200 nucleotides long and encodes 1.5 copies of the telomeric repeat sequence. The sequence of bits 43 to 51 is CAACCCCAA encoding exactly one GGGGTT.
The telomerase RNA genes of mice and humans are 65 identical, with a template of 89 nucleotide sequences, and human telomerase RNA (hTR) consists of 450 nucleotides. The template region is CUAACCCUAAC (5'3' direction. ShippenLentz (1990) cloned the telomerase RNA sequence of Euphorbia, which included the 5'CAAAACCCCAAA3' template sequence. This template is also related to the base telomeric repeat sequence (TTTTGGGG) n synthesizes RNA sequences in a base-complementary manner. Research also believes that the template in telomerase RNA is complementary to the 1.5 (TTTTGGGG) repeat sequence each time, and then the next synthesis is carried out through the sliding of the template.
In terms of telomere-binding proteins, as early as 1986 Gottschling et al. had identified telomere-binding proteins with relative molecular masses of 55,000 and 26,000 from Oxytricha. This protein specifically recognizes and binds to Oxytricha. PAP1 (repressor activator protein1) is an essential factor involved in the regulation of telomere length. One RAP1 molecule binds to an average of 18 telomeric DNA sequences, and it negatively regulates telomere length in yeast and other clones. After the gene encoding the catalytic subunit of the protein part of the enzyme, the gene encoding the catalytic subunit of the protein part of human telomerase has also been cloned and identified, named hTERT (human Telomerase Reverse Tranase) gene. This gene contains a telomerase-specific group. (telomerasespecific motif), which translates a 48-amino acid protein sequence. Controlled expression studies of hTR and hTERT genes showed that hTR gene can be expressed in non-mortal cells with forced proliferation, while hTERT gene is only expressed in tumors. Expressed in immortalized cells. Therefore, the hTERT gene has shown potential application value in tumor-specific diagnosis and treatment.
In addition, human HPV (HPV) can cause human tumors. Cervical cancer. The oncogene E6 in the HPV virus genome plays an important role in tumorigenesis. It is the first oncogene found to activate telomerase and regulate MYC at the post-transcriptional level. expression, and then MYC activates telomerase. Recently, it was discovered that estrogen in the human body can bind to an incomplete palindrome structure at position 2677 of the TERT gene promoter region and directly regulate the activity of the TERT gene. Diol can also indirectly promote the expression of TERT gene and increase the activity of telomerase by activating the expression of myc gene.
Recent comparative studies have found that many telomere proteins have very similar structures and similar functions. All in all, with the continuous deepening of research, the characteristics and functions of the telomere binding protein structure and the binding of telomere sequences will be gradually discovered and clarified. 6 Nobel Prize
According to the official website of the Nobel Foundation, Nobel Prize. Bell Karolinska Institutet in Sweden announced that the 2009 Nobel Prize in Physiology or Medicine will be awarded to Elizabeth (Liz) Helen Blackburn of the University of San Francisco, California, USA, and Johns Hopkins Medicine, Baltimore, USA. Carol Greider of the hospital and Jack Szostak of Harvard Medical School in the United States. They discovered that telomerase, a natural shedding of chromosomes produced by the root cap of chromosomes, causes aging and cancer. 7 Assays 7.1 Normal values ??
Dot blot: None. 7.2 Significance of laboratory results
Increased levels: liver cancer (93.88OD/30μg protein), tissue surrounding cancer (24.09OD/30μg protein).
7.3 Test materials
Blood 7.4 Test methods
Tumor immunoassay 7.5 Test categories