According to the latest findings from researchers of the Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch of the Helmholtz Association, Germany, control mainly occurs in the cytoplasm of the cell and not in the 'high-security tract' of the cell nucleus. Their results also highlight where gene expression (the activation of a gene for protein production) can get out of control. This study was researched by a team of scientists led by biologists Björn Schwanhäusser and Matthias Selbach, biomathematician Jana Wolf (all from MDC) and the biotechnologist Wei Chen of the Berlin Institute for Medical Systems Biology (BIMSB) of the MDC.
As described in my previous post, transcription is the process of creating a complementary RNA copy of a sequence of DNA. Translation is the process that converts an mRNA sequence into a string of amino acids that form a protein. Both of these processes work in cohesion with one another to go through the journey from DNA sequence to a functional protein. The researchers questioned which of the two processes (transcription or translation) plays the dominant role in regulating cellular protein levels.
To answer this question the MDC researchers measured the turnover of cellular mRNAs and proteins and mRNA and protein levels as their starting point. They used high-throughput technologies such as quantitative mass spectrometry and the latest sequencing techniques. In total, they evaluated proteins and mRNAs for more than 5,000 genes. The researchers drew conclusions from the collected data about the control of protein levels by using mathematical modeling. They observed that cellular protein levels mainly depend on translation of mRNAs in the protein factories of the cytoplasm.
The researchers found that cells use their resources very efficiently. Most mRNAs and proteins of abundantly expressed housekeeping genes (these genes maintain the normal operations of the body) are very stable. This is good because the cells will save worthy energy for future needs. However, the proteins responsible for rapid signaling processes are usually unstable. Therefore, cells can quickly adapt to changes in their surroundings. This may also explain why the decisive control step takes place in the cytoplasm and not in the nucleus.
According to Matthias Selbach, "so far, this is purely basic research. But we also know that the production of proteins is disturbed in many diseases, for example cancer." There is not much information about where the process gets out of control. Until now, researchers focused mainly on the nucleus to find answers to this question. However, the new findings show that the protein factories in the cytoplasm have great significance.
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