Scientists from the Florida campus of The Scripps Research Institute have identified a series of intricate biochemical steps that lead to the successful production of proteins, the basic working units of any cell.
The study, which appears in the July 6, 2012 edition of the journal Cell, sheds light on the assembly of a structure called the ribosome, a large and complex protein-producing machine inside all living cells. Ribosomes are the targets of many commercially used antibiotics and represent a promising area of research because of the importance of ribosome assembly and function for cell growth. There are well-established links between defects in ribosome assembly and cancer, making this pathway a potential new target for anti-cancer drugs.
"With important cellular machines like ribosomes, it makes sense that some process exists to make sure things work correctly," said Katrin Karbstein, a Scripps Research associate professor who led the study. "We've shown that such a quality control function exists for ribosomal subunits that use the system to do a test run but don't produce a protein. If the subunits don't pass, there are mechanisms to discard them."
Protein Production Line
As part of the protein-production process called "translation," the ribosome decodes information carried in messenger RNA (mRNA) to produce a protein-a chain of amino acids.
To produce mature, functioning ribosomal RNAs (rRNAs), the body first makes precursor rRNAs that can be processed into mature ones. In human cells, this is done in two stages-the first occurs in the nucleolus, a protein-nucleic acid structure inside the nucleus, and finally in the cytoplasm, the basic cellular stew where protein translation occurs.
In the cytoplasm, these pre-mature ribosomal subunits encounter large pools of mature subunits, messenger RNA, and numerous assembly factors and translation factors that help complete the process.
During the final maturation process, various assembly factors prevent the translation process from acting on the subunits prematurely, which would result in their rapid degradation or in the production of incorrectly assembled proteins, both processes with potentially lethal outcomes for the cell.
Trial Run