Soluble tubulin is locally enriched at mitotic centrosomes in C. elegans

Abstract

During mitosis, the centrosome expands its capacity to nucleate microtubules. Understanding the mechanisms of centrosomal microtubule nucleation is, however, constrained by a lack of knowledge of the amount of soluble and polymer tubulin at mitotic centrosomes. Here we combined light microscopy and serial-section electron tomography to measure the amount of dimer and polymer at mitotic centrosomes in early C. elegans embryos. We show that a C. elegans one-cell stage centrosome at metaphase contains more than ten thousand microtubules with a total polymer concentration of 230 µM. Centrosomes concentrate soluble a/b tubulin by about tenfold over the cytoplasm, reaching peak values of 470 µM, giving a combined total monomer and polymer tubulin concentration at centrosomes of up to 660 µM. These findings support in vitro data suggesting that microtubule nucleation in C. elegans centrosomes is driven in part by concentrating soluble tubulin.

Asymmetric Molecular Architecture of the Human γ-Tubulin Ring Complex

“…This would provide a self-regulating mechanism for limiting the size and total number of g-TuRC assemblies, and, therefore, microtubule initiation sites in cells (Brinkley et al, 1981). Such microtubule ''bookkeeping'' could be important for controlling microtubule architecture and numbers in, e.g., branched microtubule networks (Goshima et al, 2008) or in biomolecular condensates in the centrosome (Woodruff et al, 2017) and liquid-like spindle domains (So et al, 2019), which can concentrate tubulin and associated factors to incredibly high levels that would be difficult to regulate (Baumgart et al, 2019). Our study provides a foundation for dissecting how the g-TuRC assembles and functions in diverse cellular contexts.…”

c-Rel gain in B cells drives germinal center reactions and autoantibody production

“…Bulk SCRB-seq (58,59) RNA sequencing libraries were generated as previously described (60), with minor modifications. First, RNA was purified using magnetic beads (GC Biotech) and eluted in reverse tran-School of Medicine, Technical University of Munich.…”

Asymmetric molecular architecture of the human γ-tubulin ring complex

“…We propose that a low concentration of compositionally diverse subunits could provide a self-regulating mechanism for limiting the number of -TuRC assemblies, and, therefore, microtubule initiation sites 48 , in human cells. Such microtubule "book-keeping" could be important for controlling microtubule architecture and numbers in, e.g., branched microtubule networks 9 , or in biomolecular condensates in the centrosome 49 and liquid-like spindle domains 8 , which can concentrate tubulin and associated factors to incredibly high levels that would be difficult to regulate 50 . Our study provides a foundation for dissecting how the -TuRC assembles and functions in diverse cellular contexts.…”