Congrats to Erica Colicino for her cover at Cytoskeleton

by Heidi Hehnly in ,


Check out Erica’s recent publication in Cytoskeleton titled “Regulating a key mitotic regulator, polo-like kinase 1 (PLK1)”. You can find the article here. Here’s her beautiful cover below, which is a Structured Illumination Microscopy Micrograph of PLK1 (Fire Look-up Table) and kinetochores (CREST, white) during different stages of the cell cycle.

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"The balance between adhesion and contraction during cell division"

by Heidi Hehnly in , ,


Check out the beautiful review titled “The balance between adhesion and contraction during cell division” from Dylan Burnette’s lab, specifically Nilay Taneja, that my graduate student, Lindsay Rathbun, and I were lucky to contribute to. Featured below is a stunning Figure Nilay put together. It’s fantastic and shows the power of Structured Illumination Microscopy.

Figure 1.  (a)  Structured illumination microscopy micrograph of HeLa cell at  metaphase , stained for α-tubulin (yellow),  actin filaments  (magenta) and  myosin  IIA (cyan). The  mitotic spindle  comprises spindle microtubules, that facilitate  chromosome segregation  and dictate furrow positioning, and  astral microtubules  that play a pivotal role in spindle positioning by interacting with the  actin  cortex. Myosin II is uniformly distributed at the cortex during metaphase.  (b)  Upon  anaphase  onset, myosin II is enriched at the equator to ingress the  cleavage furrow . Note the extensive contacts between the mitotic spindle and the contractile cortex, suggesting cross-talk between these two  cytoskeletal  networks. Note that the actin bundles protruding from the cells are not retraction fibers, as they are not attached to the substrate. Scale bar: 10 μm.

Figure 1. (a) Structured illumination microscopy micrograph of HeLa cell at metaphase, stained for α-tubulin (yellow), actin filaments (magenta) and myosin IIA (cyan). The mitotic spindle comprises spindle microtubules, that facilitate chromosome segregation and dictate furrow positioning, and astral microtubules that play a pivotal role in spindle positioning by interacting with the actin cortex. Myosin II is uniformly distributed at the cortex during metaphase. (b) Upon anaphase onset, myosin II is enriched at the equator to ingress the cleavage furrow. Note the extensive contacts between the mitotic spindle and the contractile cortex, suggesting cross-talk between these two cytoskeletal networks. Note that the actin bundles protruding from the cells are not retraction fibers, as they are not attached to the substrate. Scale bar: 10 μm.


Check out the new Castaneda Lab Paper that we assisted with!

by Heidi Hehnly in ,


Under stress, certain eukaryotic proteins and RNA assemble to form membraneless organelles known as stress granules. The most well-studied stress granule components are RNA-binding proteins that undergo liquid-liquid phase separation (LLPS) into protein-rich droplets mediated by intrinsically disordered low-complexity domains (LCDs). Here we show that stress granules include proteasomal shuttle factor UBQLN2, an LCD-containing protein structurally and functionally distinct from RNA-binding proteins.  In vitro , UBQLN2 exhibits LLPS at physiological conditions. Deletion studies correlate oligomerization with UBQLN2’s ability to phase-separate and form stress-induced cytoplasmic puncta in cells. Using nuclear magnetic resonance (NMR) spectroscopy, we mapped weak, multivalent interactions that promote UBQLN2 oligomerization and LLPS. Ubiquitin or polyubiquitin binding, obligatory for UBQLN2’s biological functions, eliminates UBQLN2 LLPS, thus serving as a switch between droplet and disperse phases. We postulate that UBQLN2 LLPS enables its recruitment to stress granules, where its interactions with ubiquitinated substrates reverse LLPS to enable shuttling of clients out of stress granules.

Under stress, certain eukaryotic proteins and RNA assemble to form membraneless organelles known as stress granules. The most well-studied stress granule components are RNA-binding proteins that undergo liquid-liquid phase separation (LLPS) into protein-rich droplets mediated by intrinsically disordered low-complexity domains (LCDs). Here we show that stress granules include proteasomal shuttle factor UBQLN2, an LCD-containing protein structurally and functionally distinct from RNA-binding proteins. In vitro, UBQLN2 exhibits LLPS at physiological conditions. Deletion studies correlate oligomerization with UBQLN2’s ability to phase-separate and form stress-induced cytoplasmic puncta in cells. Using nuclear magnetic resonance (NMR) spectroscopy, we mapped weak, multivalent interactions that promote UBQLN2 oligomerization and LLPS. Ubiquitin or polyubiquitin binding, obligatory for UBQLN2’s biological functions, eliminates UBQLN2 LLPS, thus serving as a switch between droplet and disperse phases. We postulate that UBQLN2 LLPS enables its recruitment to stress granules, where its interactions with ubiquitinated substrates reverse LLPS to enable shuttling of clients out of stress granules.