Emmanuel Nsamba

All Publications

• Tubulin isotypes - functional insights from model organisms. Journal of cell science Nsamba, E. T., Gupta, M. L. 2022; 135 (9)

  Abstract

  The microtubule cytoskeleton is assembled from the alpha- and beta-tubulin subunits of the canonical tubulin heterodimer, which polymerizes into microtubules, and a small number of other family members, such as gamma-tubulin, with specialized functions. Overall, microtubule function involves the collective action of multiple alpha- and beta-tubulin isotypes. However, despite 40 years of awareness that most eukaryotes harbor multiple tubulin isotypes, their role in the microtubule cytoskeleton has remained relatively unclear. Various model organisms offer specific advantages for gaining insight into the role of tubulin isotypes. Whereas simple unicellular organisms such as yeast provide experimental tractability that can facilitate deeper access to mechanistic details, more complex organisms, such as the fruit fly, nematode and mouse, can be used to discern potential specialized functions of tissue- and structure-specific isotypes. Here, we review the role of alpha- and beta-tubulin isotypes in microtubule function and in associated tubulinopathies with an emphasis on the advances gained using model organisms. Overall, we argue that studying tubulin isotypes in a range of organisms can reveal the fundamental mechanisms by which they mediate microtubule function. It will also provide valuable perspectives on how these mechanisms underlie the functional and biological diversity of the cytoskeleton.

  View details for DOI 10.1242/jcs.259539

  View details for PubMedID 35522156

• A new partial loss of function allele of rad-54.L. microPublication biology Akerib, C. C., Yokoo, R., Nsamba, E. T., Strand, L. G., Yamaya, K., Villeneuve, A. M. 2022; 2022

  Abstract

  RAD-54.L is required for the repair of meiotic double-strand DNA breaks (DSBs), playing an essential role in promoting removal of recombinase RAD-51 and normal completion of meiotic recombination. Failure to complete meiotic DSB repair leads to 100% lethality of embryos produced by rad-54.L null mutant mothers. Here we report a new partial loss of function allele, rad-54.L(me139) , that may prove useful for investigating meiotic mechanisms by providing a sensitized genetic background that reduces but does not eliminate the essential functions of RAD-54.L.

  View details for DOI 10.17912/micropub.biology.000637

  View details for PubMedID 36247323

• Tubulin isotypes optimize distinct spindle positioning mechanisms during yeast mitosis. The Journal of cell biology Nsamba, E. T., Bera, A., Costanzo, M., Boone, C., Gupta, M. L. 2021; 220 (12)

  Abstract

  Microtubules are dynamic cytoskeleton filaments that are essential for a wide range of cellular processes. They are polymerized from tubulin, a heterodimer of alpha- and beta-subunits. Most eukaryotic organisms express multiple isotypes of alpha- and beta-tubulin, yet their functional relevance in any organism remains largely obscure. The two alpha-tubulin isotypes in budding yeast, Tub1 and Tub3, are proposed to be functionally interchangeable, yet their individual functions have not been rigorously interrogated. Here, we develop otherwise isogenic yeast strains expressing single tubulin isotypes at levels comparable to total tubulin in WT cells. Using genome-wide screening, we uncover unique interactions between the isotypes and the two major mitotic spindle positioning mechanisms. We further exploit these cells to demonstrate that Tub1 and Tub3 optimize spindle positioning by differentially recruiting key components of the Dyn1- and Kar9-dependent mechanisms, respectively. Our results provide novel mechanistic insights into how tubulin isotypes allow highly conserved microtubules to function in diverse cellular processes.

  View details for DOI 10.1083/jcb.202010155

  View details for PubMedID 34739032