Yale Researchers Provide New Insight into Cell Growth

Yale researchers have discovered a new cellular entity, called the SSU processome, that challenges their previous ideas about how ribosomes are made and brings them closer to understanding how uncontrolled cell growth can lead to many human diseases, including cancer.

“Understanding how cells grow and divide has fascinated scientists since cells were first visualized using a microscope,” said the study’s author, Susan Baserga, M.D., associate professor of molecular biophysics and biochemistry, therapeutic radiology and genetics at Yale. “Studying cell growth and division are two of the most important areas of scientific research today.”

In order for cells to survive, they need to make many proteins. In her lab, Baserga and her co-workers study how ribosomes, parts of the cell responsible for making all proteins, are themselves made. Using state-of-the-art techniques, Baserga and her team, which includes collaborators at the University of Virginia, discovered and purified a cellular “machine” that is required for making ribosomes.

“We call this complex the SSU processome because it is essential for processing the RNA that becomes part of the ribosome,” said Baserga. ” The SSU processome is a complex of RNA and many proteins. Of these proteins, we identified 17 that had never been described before. The large size of the SSU processome was completely unexpected, and challenged our preconceived ideas about how ribosomes are made.”

Baserga now believes that the SSU processome and its proteins play an important role in helping ribosomes establish their final shape.

“Since the SSU processome plays such a critical role in cell growth, we suspect that small alterations in these proteins may be involved in diseases that are not yet well understood,” said Baserga.

Since the study was published in the June 27 issue of Nature, Baserga and her co-workers have found further evidence to bolster their original findings. They have identified 12 additional protein components of the SSU processome, including 5 proteins, which are components of the mature ribosome.

“This suggests that the SSU processome, in addition to processing RNAs, also assembles ribosomes,” said Baserga.

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Karen N. Peart: karen.peart@yale.edu, 203-432-1326