The Rog Lab

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.

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).

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.

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.

We also performed a CheC-PLS on isolated nuclei, using Rec8-GFP and nanobodies targeted to GFP and tethered to a methyltransferase. (This variation is related to recently published techniques like DiMeLo-seq and SAMOSA). Cc @vram142 @astraight

#1: CheC-PLS (pronounced ‘check, please’) is a new genomic technique. It relates to ChIP, but adds 4 crucial features: 1. contiguity (how distant events are regulated) 2. history (where a protein has been) 3. heterogeneity (single cell data) 4. context (mapping repeats).

The story starts with a saturated suppressor screen for a temperature-sensitive mutation that destabilizes the SC. Lisa identified dozens of suppressors, that all mapped to three short stretches in SC proteins.

Thrilled to have this out! And David's beautiful drawing is on the cover! molbiolcell.org/doi/10.1091/… (pdf here: theroglab.org/publications ) cc: @janetiwasa @dsgoodsell @MargotRiggi @nothingtolius Hyun Kate Lee and Simon Curie

What a great way to (almost) wrap up the semester: a seminar and hike with @sarperotto

Haunted trail

This reminded us of the classic images by Adelide Carpenter & this idea was also consistent with recent work from @adernburg @Raph_Mercier @ChrisMorgan555 @KBomblies and others on coarsening of recombination nodules & diffusion of their components within the SC. 11/12

Finding 2: We expected that the SC relies on its conserved localization btw the parental chromosomes to promote exchanges. But it doesn’t: the SC can promote formation of recombination nodules whether it is between the chromatid undergoing an exchange or next to them! 10/12

An interesting point: repair events btw sisters and btw parental chromosomes are regulated in similar ways: both prefer to form non-exchanges; both are promoted by recombination nodules; and both exhibit interference. 8/12