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.
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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.