Biochemical controls: controlling DNA in cell division (Introduction)

by David Turell , Saturday, March 30, 2024, 22:01 (30 days ago) @ David Turell

Coordinated proteins and enzymes at work:

https://phys.org/news/2024-03-scientists-key-quality-mechanism-dna.html#google_vignette

"Now, in a landmark finding, biologists from the Perelman School of Medicine at the University of Pennsylvania and from the University of Leeds have identified a multi-protein "machine" in cells that helps govern the pausing or stopping of DNA replication to ensure its smooth progress.

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"The DNA replication process is carried out by multiple protein complexes with highly specialized functions, including the unwinding of DNA and the copying of the two unwound DNA strands. The process is akin to a factory assembly line where balls made up of massive, crumpled strings of data are unraveled, allowing specific pieces to be trimmed and copied. Biologists know a good deal about how this process starts and proceeds, but know less about how it is stopped or paused.

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"In the study, the researchers used cryo-electron microscopy, CRISPR-based mutation analyses, and other advanced techniques to identify a protein complex that has a central replication-stopping role for the lagging strand.

"They showed that this four-protein machine, which they call 55LCC, binds to DNA and its associated replication complex. Powered by two motor-like enzymes called ATPases, 55LCC appears to unfold the tightly folded replication complex, allowing it to be chopped up by protein-snipping enzymes and cleared away.

"The experiments suggested that this stopping or pausing function of 55LCC is crucial for the smooth progression of DNA replication. When 55LCC is absent, the investigators found, replication is likely to become stuck, and affected cells cease dividing.

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"55LCC may also turn out to be a more general tool for protein recycling—another process critical to the health of cells. Greenberg and his team are continuing to study how 55LCC works and is regulated, including understanding the precise signal that tells 55LCC to become active and start unfolding a DNA replication complex."

Comment: every biochemical reaction in the cells is carefully monitored by very complex sets of proteins and enzymes. It is definitely very difficult to ignore the obvious purpose in these mechanisms.