Biochemical controls: intracellular reactions II (Introduction)

by David Turell , Thursday, December 21, 2023, 20:38 (128 days ago) @ David Turell

A different intracellular study:

https://phys.org/news/2023-12-reveals-hidden-power-intracellular-neighborhoods.html

"New findings published in Molecular Cell provide details about the hidden organization of the cytoplasm—the soup of liquid, organelles, proteins, and other molecules inside a cell. The research shows it makes a big difference where in that cellular broth, messenger RNA (mRNA) gets translated into proteins.

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"Most of the well-known components inside a cell have a defined shape and come wrapped in an exterior membrane: the nucleus, mitochondria, lysosomes, the Golgi apparatus.

"Two of the key components at the heart of the Mayr team's study don't have membranes—which is what has made them so hard to find in the first place, and a challenge to isolate and study in the lab.

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"The new study demonstrated that where in the cytoplasm this translation step happens isn't random, and that there's an underlying logic or "code" that directs mRNAs to specific neighborhoods within the cell.

"'The whole cytoplasm is nicely compartmentalized," Dr. Mayr says. "We were able to demonstrate there is a code at work that's based on the mRNA's biophysical features—their size and shape—and the particular RNA-binding proteins they partner with. This code directs the mRNAs to different locations for translation."

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"...the research team was able to show that mRNAs of different lengths and shapes tend to gravitate to specific neighborhoods. And that if you intervene to redirect them to a different location, it can have a profound impact on the amount of protein that gets produced and on the protein's function.

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"The researchers looked at mRNAs that are located on the surface of the endoplasmic reticulum (an organelle involved in protein synthesis and other cellular functions). It's well established that proteins associated with cellular membranes and those that get secreted by the cell for use elsewhere are translated there.

"The research revealed that nearly 15% of mRNAs that encode non-membrane proteins are also translated at the ER—and they encode large and highly expressed proteins.

Meanwhile, the mRNAs that get translated in the cytosol (the liquid part of the cytoplasm) tend to be very small proteins. (my bold)

"And mRNAs that locate to TIS granules tend to be transcription factors (proteins that regulate the transcription of genes). TIS granules are a membrane-less cellular component Mayr's lab discovered in 2018. They form a network of interconnected proteins and mRNAs, and are closely allied with the endoplasmic reticulum, forming a distinct space where mRNA and proteins can collect and interact.

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"'Our data show that if you translate an mRNA in the TIS granules, the resulting protein will perform one function, and if you translate it outside of the TIS granules, it will perform a different function," she says. "And this is how, in higher organisms like us, one protein can have more than one function." (my bold)

"One specific protein the team examined during the study is MYC. The MYC gene is one of the more famous oncogenes, and mutations in MYC underlie the development of many cancers.

"'We observed that several MYC protein complexes were only formed when MYC mRNA was translated in the granules and not when it was translated in the cytosol," Dr. Mayr says. "Our results show there's an important biological relevance to these neighborhoods, even when only about 20% of mRNAs get translated in the TIS granules."

"Together, these insights suggest that mRNA could be targeted to achieve different functions, as well as to vary the amount of a protein that gets produced, she adds."

Comment: once again, this study shows how the cells are highly organized and controlled by genetic messengers. An ID view would denote each organelle as IC in order to perform its special functions.