Discovery provides scientists with a better understanding of limiting uncontrolled cell growth -
Biologists at UC San Diego have found the "missing link" in the chemical system that allows to animal cells to produce ribosomes -the thousands of protein "factories" contained in each cell that produce all the proteins necessary for tissue building and maintaining life.
Their discovery, detailed in the June 23 issue of Genes & Development, will not only force a revision of basic textbooks on molecular biology, but also to provide scientists a better understanding of how to limit the uncontrolled cell growth, such as cancer, which may be adjusted by controlling the release of ribosomes.
ribosomes are responsible for the production of wide variety of proteins including enzymes; structural molecules, such as hair, skin and bones; hormones such as insulin; and components of the immune system such as antibodies. Considered the most important molecular machinery of life, ribosomes have been extensively studied by scientists (the 09 Nobel Prize in chemistry, for example, was awarded for the study of structure and function). But until now, researchers had not discovered the details of how proteins that are used to build ribosomes themselves are produced.
Among the multicellular animals, such as humans, the ribosomes are composed of about 80 different proteins (humans have 79 while other animals have a slightly different number), and four different kinds of molecules RNA. In 1969, researchers discovered that synthesis of ribosomal RNA is carried out by specialized systems using two key enzymes: RNA polymerase I and RNA polymerase III. But until now, scientists did not know whether a complementary system was also responsible for the production of 80 proteins that make up the ribosome.
This is essentially what the UC San Diego researchers led by Jim Kadonaga, biology teacher, set out to examine. What they found was the missing link-specialized system that allows ribosomal proteins themselves to be synthesized by the cell.
"We found that the ribosomal proteins are synthesized via a novel regulatory system with the enzyme RNA polymerase II and a factor called TRF2" said Kadonaga. "In the production of most proteins, RNA polymerase II works with a factor called TBP, but for the synthesis of ribosomal proteins, it uses TRF2".
"The discovery of this system based on specialized TRF2 for ribosome biogenesis," he added, "provides a new way to study ribosomes and control of cell growth, and should lead to understanding and potential treatment of diseases like cancer. "
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