Biologists have found the "missing link" in the chemical system that enables animal cells to produce ribosomes - the thousands of protein factories in each cell that manufacture all of the proteins needed to build tissue and sustain life.Their discovery provides scientists with a better understanding of how to limit uncontrolled cell growth, such as cancer, that might be regulated by controlling the output of ribosomes."The discovery of this specialised TRF2-based system for ribosome biogenesis provides a new avenue for the study of ribosomes and its control of cell growth," said Jim Kadonaga, a professor of biology at University of California at San Diego in the US."It should lead to a better understanding and potential treatment of diseases such as cancer," he said.Ribosomes are responsible for the production of the wide variety of proteins that include enzymes; structural molecules, such as hair, skin and bones; hormones like insulin; and components of our immune system such as antibodies.
Regarded as life's most important molecular machine, ribosomes have been intensively studied by scientists.In 1969, scientists discovered that the synthesis of the ribosomal RNAs is carried out by specialised systems using two key enzymes: RNA polymerase I and RNA polymerase III.But until now, scientists were unsure if a complementary system was also responsible for the production of the 80 proteins that make up the ribosome."We found that ribosomal proteins are synthesised via a novel regulatory system with the enzyme RNA polymerase II and a factor termed TRF2," Kadonaga said."For the production of most proteins, RNA polymerase II functions with a factor termed TBP, but for the synthesis of ribosomal proteins, it uses TRF2," Kadonaga said.The study appeared in the journal Genes & Development.