Immune complexity: meiosis phase (Introduction)

by David Turell , Thursday, March 18, 2021, 14:07 (1133 days ago) @ David Turell

Amazingly exact and complex:

https://www.nature.com/articles/d41586-021-00512-2?WT.ec_id=NATURE-202103&sap-outbo...

"Accurate chromosome segregation in meiosis requires that each chromosome first identify and physically link to its homologous partner. These steps depend on a DNA-repair pathway called homologous recombination, which begins with programmed DNA breakage at a few randomly chosen sites along each chromosome. The broken DNA ends seek out similar sequences on other chromosomes, eventually identifying their homologous partner and establishing physical links called crossovers. Crossovers also enable the exchange of genetic information between homologous chromosomes, ensuring genetic variation between parents and offspring.

"The molecular mechanisms that control homologous recombination in meiosis have been studied for more than two decades, since the identification of a set of ten proteins in the budding yeast Saccharomyces cerevisiae that are required for the formation of DNA breaks during meiosis2. Four of these proteins make up the Spo11 core complex which breaks DNA. Three others form the MRX complex, which mediates post-breakage processing steps2. The roles of the remaining three proteins — Rec114, Mei4 and Mer2, together called the RMM complex — have remained mostly mysterious.

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"The authors purified the S. cerevisiae RMM complex for the first time, revealing that Rec114 and Mei4 form a subcomplex that associates with Mer2. The authors then showed that the purified RMM proteins can condense on DNA into liquid-like droplets containing hundreds of copies of each protein.

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"Taking advantage of this purified complex in the current work, the group showed that RMM condensates recruit the Spo11 core complex to DNA. A mutation in Rec114 that disrupts its binding to the Spo11 core complex also compromises DNA breakage in meiotic cells, indicating that the RMM complex recruits the Spo11 core complex to DNA break sites.

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"Claeys Bouuaert and colleagues’ work marks the start of an exciting ‘phase’ of research into the fundamental mechanisms of meiotic recombination. Taken together with steady progress in our understanding of meiotic chromosome architecture and dynamics, the stage is set for further advances,..."

Comment: Mind-blowing c0mpexity. Not presented for full understanding but a glimpse into the intricate dance of these molecules. Only design fits.