Genome complexity: copy accuracy controls (Introduction)

by David Turell , Thursday, August 16, 2018, 19:27 (2292 days ago) @ David Turell

The molecules that control cell memory in cell division are found:

https://phys.org/news/2018-08-scientists-technology-key-puzzle-cellular.html

"Cells divide constantly throughout life. But how do cells remember whether to develop into skin, liver or intestinal cells? It's a question that has puzzled scientists for many years. Now, scientists from the Faculty of Health and Medical Sciences and the Faculty of Sciences at the University of Copenhagen have come a little closer to understanding this process.

"They have developed a technique that gives new insight into epigenetic cellular memory. With the new technique, called SCAR-seq, the researchers have been able to address how epigenetic information stored in histone proteins is transmitted when DNA is copied and cells divide.

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"Inside the human cell, our DNA is wrapped around histone proteins. Together, they form a structure called chromatin. When a cell divides, it is crucial that both the DNA and the entire chromatin structure are copied accurately. Chromatin stores epigenetic information that affects which genes are to be expressed. That is, the epigenetic information in our cells helps to control which genes are "turned on" and "off."

"In the new study, the researchers have studied embryonic stem cells from mice. With SCAR-seq, it has become possible for the researchers to identify a protein that is responsible for transfer of histone proteins from the old DNA strand to the two new DNA strands during replication—namely MCM2.

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"'It has been a recurring question whether the transfer of histones with their chemical modifications was completely random during DNA replication. In our study, we show that it is not a random but a highly controlled process. Our data show that the histones have a preference for one DNA strand, the so-called leading strand, but that MCM2 counteracts this bias and ensures that there is almost symmetry between the two new DNA strands, that is, an even distribution of histone-based information."

"'When we disrupted that mechanism, all histone-based information was transferred to one DNA strand, namely the leading strand, and not to the other, lagging strand. This means that this function by MCM2 is essential for the two new DNA strands to receive the same information stored in histones," says co-author of the study Robin Andersson."

Comment: Uncovering teh extreme complexity one layer at a time. Copy protections had to exist at the origin of life. Only design fits.