The research work of these three scientists is consistent, and they have made the same contribution in revealing the molecular mechanism of cell cycle regulation. Hartwell was the first person to pay attention to the cell cycle and try to explore its control mechanism.
Engels called the cell theory established in19th century one of the three great discoveries of that century. Cells are structural units and functional units of organisms. All living things are made up of cells that reproduce through division. An adult has about 100 trillion cells, and these cells are all derived from a fertilized egg cell. At the same time, a large number of cells in adults are constantly dividing to produce new cells to replace those dead cells. Cell division must meet the following conditions: when the cell grows to a certain extent, it must be able to copy chromosomes and accurately transfer different chromosomes to two daughter cells. These different growth processes coordinate with each other in the cell cycle. About 10 years old, he had a strong curiosity about some things, and often collected animal specimens such as butterflies, frogs, snakes, spiders, etc., to understand some issues he was interested in. After entering high school, I am good at mathematics, physics and mechanical drawing, hoping to become an engineer. After Hartwell graduated from high school, he first entered a short-term university with 1-2 years. Seeing that he was very studious, his tutor encouraged him to transfer to California Institute of Technology. After the exam, he entered the university as a sophomore. He majored in physics in college, but he also listened to lectures on biology from time to time, especially after attending phage genetics, and he had a certain understanding of biology. In addition, he spent a lot of time studying chemistry, biochemistry and genetics, and read the original documents related to phage inheritance and gene regulation. 196 1 After graduating from university, he entered the Massachusetts Institute of Technology, studied gene regulation under BorisMagasanik, and 1964 obtained his doctorate. During this period, FrancoisJacob and JacquesMonod published their famous research on lactose operon, and hartwell decided to take the research on cell growth control as his postdoctoral work. After reading the literature, he learned that RenatoDulbecco's laboratory had conducted research in this field. From 1964 to 1965, we studied the cells infected by polyoma virus in Renato Dubberke laboratory of Shack College. 1965 Associate Professor, Irvine College, University of California; 1968, Professor, University of Washington; 1997, director of Fujimori cancer research center.
As he himself said, my impulse to study comes from wanting to know about cancer and finding out the genes that control cell division. From 65438 to 0965, Hartwell entered Irvine College of California as a faculty member. At that time, the laboratory was under construction. He looked up information in the library and found that some people used yeast for cytological and genetic research. He thinks it is better to use simple yeast as animal cell model than mammalian cells. But he knows nothing about yeast. He personally learned how to operate yeast from two masters of yeast research at the University of California at Berkeley and Donaldc at the University of Washington. Hawthorne and Herschel Roman.
In the early 1970s, he began to use Saccharymtcescerevisiae as an experimental model to study the cell cycle. He and his research team established and isolated more than 1000 temperature-sensitive mutants. These mutants can grow at room temperature, but not at 36℃. The synthesis of polymer and cell division were analyzed at limited temperature. In the study, they isolated some mutant strains that are easy to change and found that some mutations can stop at a specific cell cycle stage. Three years later, he transferred to Washington University, where several of his students continued to study the cell cycle with him. His student briand B.Reed used microprojection technology to determine which stage of the cell cycle it was in from the cell morphology. Using this method, they successfully isolated hundreds of genes involved in cell cycle regulation and named them cdc(celldivisioncycle) genes, among which cdc28 gene is particularly important. He thinks that with the help of high-resolution electron microscope, we can learn more about these genes.
His student byers took an active part in this work and proposed to observe the spindle and its polarity. They found that when the cdc28 gene mutates, the cell cycle will stop at the late "start" checkpoint of G/Kloc-0, and once the cell passes this checkpoint, it will start to replicate DNA. Therefore, they think that CDC28 protein is an important protein to control the cell from G 1 to S phase. So hartwell called cdc28 a "startup" gene. Hartwell believes that CDC28 will only play a role when the cell reaches a certain scale, but after a CDC28 event is completed, the cell will complete the remaining stage that leads to little cell growth, that is, complete a cell cycle. Therefore, cdc28 gene is necessary for specific transformation in cell cycle.
In the mid-1970s, during the hartwell research, PaulNurse and others in Britain used Saccharomyces cerevisiae as experimental materials. On the basis of hartwell's research, they also found many genes that regulate cell cycle, among which cdc2 plays an important role in cell division regulation, which controls cells from G2 phase to M phase. They isolated and cloned the cdc2 gene. 1987, Nass's team isolated the gene corresponding to cdc2 from human body and found that this gene encodes a cell cycle-dependent protein kinase (CDK protein) called by protein. Since then, they have found dozens of different CDK molecules in human body. Further research found that both cdc2 and cdc28 encode a 34KD protein kinase, which promotes cell cycle. However, genes weel and cdc25 showed inhibition and promotion of cdc2 activity, respectively. Therefore, CDK protein is a key factor in regulating cell cycle. From 65438 to 0980, members of hartwell's team and his student SteveReed cloned the cdc28 gene and established a laboratory specializing in protein kinases.
1983, TimothyHunt and Teemo used sea urchin eggs as experimental materials, and found that during the cleavage process, the contents of two kinds of protein changed with the cell cycle, and they began to synthesize at each interval, reached the peak at G2/M, disappeared suddenly after the end of m, and then re-synthesized at the next interval. He named them cyclins. Later, a similar situation was found in frogs, Xenopus laevis, sea urchins, fruit flies and yeast. Cyclin mRNA of various animals can induce frog eggs to mature. The cyclin of Xenopus laevis was purified by M. j. loh ka 1988 and identified as 32KD and 45KD proteins. The combination of these two protein can phosphorylate various protein. Later, further experiments by Nass (1990) proved that the 32KD protein was a homologue of CDC2, while the 45KD protein was a homologue of cyclinB, thus linking the research in the three fields of cell cycle. Cyclin is an essential protein in the process of cell growth and division, and its content changes with different stages of the growth and division cycle, thus affecting the role of CDK.
Further research by hartwell's team found that about 105 cells in normal yeast cells would lose a chromosome. They want to know whether any limitation of cell cycle function will change this fidelity. Together with student Davidsmith, he studied the chromosome loss, recombination and mutation in temperature-sensitive mutation when cells grow at their maximum allowable temperature, and found that the ratio of chromosome loss, recombination or mutation in most mutations greatly increased.
Leland hartwell (left)
TedWeiner of the research team used the cell cycle of yeast cells to stop synchronously under the action of radiation and inducer, and observed the radiation-sensitive mutation to determine what changes had taken place in the response of cell cycle to radiation. He soon discovered that some radiation-sensitive mutations had adapted to radiation and could not stop the cell cycle. If rad9 gene is eliminated, the regulation of radiation on cell cycle will also be eliminated, which proves the regulation of rad9 gene. Then they found other such genes. After the mutation of Rad9 gene, the chromosome loss rate increased by 20 times without any foreign DNA damage. Why does the chromosome loss rate increase? His students' findings explain this problem: because radiation produces insensitive mutations that block mitosis, cells are not sensitive to the blocking caused by DNA replication defects. This shows that errors in DNA replication occur randomly at a very low frequency, and the detection point must ensure the correct repair of the damage in these cells. Therefore, they put forward the idea that cells have "detection points". The so-called detection point means that protein, who has the regulatory function, will put the cell cycle into a pause state during this period, and the cell will check whether the DNA is damaged and repair the damage, so as to enter the next stage. Subsequently, his students found the same checkpoint gene by controlling the repair frequency of damaged DNA and the frequency of cells entering S phase when the damaged cells were at G 1.
Hartwell's important contribution to the study of cell cycle is manifested in two aspects: first, he discovered a large number of genes that control cell cycle, especially the discovery of the "starting point" gene, so that people know that this gene plays a key role in the first step of controlling each cell cycle; The second is the discovery of cell cycle detection point, which plays a vital role in ensuring the normal growth and division of cells during the cycle operation. These two findings are of great significance for fully understanding the growth process of cells and can be applied to many different fields. This study also proves that when cell cycle regulation is defective, it may lead to chromosome variation, which may eventually lead to cancer, thus opening up a new direction for the study of cancer diagnosis. In the long run, it may open up a new way for the diagnosis and treatment of cancer.