Gene regulation

Article Abstract:

The General Motors Cancer Research Foundation awarded the 1990 Alfred P. Sloan, Jr. Prize for research to Mark S. Ptashne. In his prize-winning lecture, Dr. Ptashne provides an overview of his research on gene regulation. Cells of higher organisms hold their genetic material within nuclei, organized into complex chromosomes. Such cells, called eukaryotic, are much too complicated to provide a convenient starting point for investigation. Therefore, the research began by examining how a particular virus, called a phage, infects bacteria. The genetic material of bacteria is more simply organized in these prokaryotic cells without nuclei. The phage inserts its DNA into the host DNA. A specific protein, called a repressor, prevents viral proteins from being synthesized until the proper signal is received. However, this repressor must activate at least one gene: the gene to make more copies of itself. Ptashne was able to learn how the molecular structure of this repressor protein has two activities, one which binds to a specific DNA sequence and another which activates the transcription of the adjacent gene. Armed with the knowledge of the prokaryotic repressor protein, researchers then tackled the corresponding process in yeast, one of the smallest, if not the simplest, of all cells with a nucleus. They found that a similar process is at work, but that important distinctions exist. The gene activating the protein in the yeast also has two activities, one which binds DNA and the other which activates the gene. Indeed, it is possible to piece together artificial proteins which have one or the other activity, but not both. However, unlike the simpler prokaryotes, the eukaryotic activator is capable of activating genes that are far away: in an extreme case, as far away as 1,000 DNA base pairs. How this action occurs remains mysterious, but it seems that the DNA forms a large loop so the activator can contact a target site right next to the gene to be controlled. Ptashne suggests that the ultimate control of the gene might result from the contact of several activators with several target sites. Not only would this mechanism provide a means to control far-away genes, but it would also provide eukaryotic cells with a wide range of activators to choose from in the organization of the molecular events within the nuclei. (Consumer Summary produced by Reliance Medical Information, Inc.)

Enzymes, Genetic regulation, Genetic transcription, Operons, Transcription (Genetics), Cellular control mechanisms, Cell regulation

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Summing up

Article Abstract:

Ageing was described as a dynamic process which starts to occur at 30 and proceeds at a variable rate. The more research is done in aging, the more it is that people realize a lot is still to be learned about the aging process. Aging research has also shown valuable contribution to the improvement of the quality of life of people especially in the later years. Furthermore, most of its findings lend a clearer pespective of certain disease entities such as cardiovascular disease which were postulated to have its roots in fetal life.

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A DNA chip off the aging block

Article Abstract:

Using DNA microarray analysis, researchers showed that about 1% of the genes in fibroblasts have different patterns of expression depending on the age of the individual. However, the study only included seven people, and must be replicated in larger groups before differences in gene expression can be linked to aging.

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