RT @EToraason: The last of my graduate work with @DianaLibuda is out in @eLife! We show that BRCA1 and SMC-5/6 regulate DNA break repair pa….

RT @J_Cell_Sci: In their Review, Iván Olaya, @smburgessucd @BurgessLab and Ofer Rog @TheRogLab discuss the formation and resolution of meio….

RT @BurgessLab: We are pleased to report the publication of our review on the formation and resolution of meiotic chromosome entanglements….

RT @GeneticsGSA: TOMORROW, 1pm EDT📣 Ofer Rog of @UoUBiology will cover 2 unpublished stories from his lab on unexpected de-mixing of sister….

RT @GeneticsGSA: 🗓️ July 11, 1pm EDT: Ofer Rog of @UoUBiology will cover 2 unpublished stories from his lab on the….

We’d love to get feedback and suggestions. Kudos to Kewei, an amazing grad student who developed CheC-PLS over the last 5 years; to Chloe and @lexy_von_diez (now with her own lab, new-car-smell and all, at UMinnesota); and to @LisaKursel and a super-talented undergrad, Kaan.

So Skp1 has been moonlighting for >100 million years. Which adds a new twist to the SC paradox: how does a highly conserved protein (Skp1) maintains intimate interaction with quickly diverging proteins in a way that does not leave a clear evolutionary mark in their sequence?.

In both nematode, Skp1 is not only necessary for assembly of the SC onto chromosomes - without dimerization-competent Skp1, SC proteins are absent.

Lisa turned to the distantly related nematode P. pacificus, and found that the answer is a resounding ‘yes’. Ppa-SKR-1 localize to the middle of the SC, and a conserved dimerization interface in Skp1 is specifically required for SC assembly in Pristi, as it is in elegans.

Recently, @WormMeiosis made an intriguing discovery: Skp1, a conserved subunit of the SCF ubiquitin ligase complex (SKR-1 in C. elegans), moonlights as a structural component of the SC. @LisaKursel decided to test whether this function is conserved.

On the other hand, the protein sequence is incredibly divergent between and within clades, so much so that the genes had to be independently cloned in different model organisms. (More on that in Lisa’s previous paper.)

#3: Skp1 in the SC. SC proteins have intriguing evolutionary history: they build a highly conserved structure AND (almost) all subunits are co-dependent for assembly.

That has crucial implications: ZHP-3 can sample the entire 6um chromosome in tens of minutes, whereas SYP-3 cannot. By extension, ZHP-3 is capable of efficiently transducing a crossover signal, whereas SYP-3 would be unlikely to.

The second important finding came from comparing the diffusion of an SC component (SYP-3) vs a regulator of crossovers (ZHP-3). ZHP-3 diffuses 4-9 times faster than SYP-3 (depending on meiotic stage).

(Black-boxing some amazing tech here; check out the preprint for details.) This finding confirmed a crucial aspect of the coarsening hypothesis.

However, a crucial piece of this model has not been tested: do molecules diffuse within the SC? @lexy_von_diez directly tested that. By sparsely labeling SC components and crossover regulators, she was able to observe single molecules in live gonads.

This idea, and beautiful data from worms and plants (cc @Raph_Mercier @ChrisMorgan555 ) suggested coarsening regulates genetic exchanges (crossovers).

#2: Diffusion within the synaptonemal complex (SC). A few years ago Abby Dernburg and I showed the SC has liquid properties.

And perhaps not less important - potential for many future experiments. Should be noted: nothing in the design confines CheC-PLS to budding yeast, so it should be adaptable to other model organisms.

Our data revealed sliding of cohesin on DNA (presumably loop extrusion); positioning of nucleosomes; and, AFAIK, the first binding patterns of cohesins in the rDNA locus. Much more data inside.