Nuclear Size Is Regulated by Importin α and Ntf2 in Xenopus

Abstract

SUMMARY The size of the nucleus varies among different cell types, species, and disease states, but mechanisms of nuclear size regulation are poorly understood. We investigated nuclear scaling in the pseudotetraploid frog Xenopus laevis and its smaller diploid relative Xenopus tropicalis, which contains smaller cells and nuclei. Nuclear scaling was recapitulated in vitro using egg extracts, demonstrating that titratable cytoplasmic factors determine nuclear size to a greater extent than DNA content. Nuclear import rates correlated with nuclear size, and varying the concentrations of two transport factors, importin α and Ntf2, was sufficient to account for nuclear scaling between the two species. Both factors modulated lamin B3 import, with importin α increasing overall import rates and Ntf2 reducing import based on cargo size. Importin α also contributes to nuclear size changes during early X. laevis development. Thus, nuclear transport mechanisms are physiological regulators of both interspecies and developmental nuclear scaling.

Paternal chromosome loss and metabolic crisis contribute to hybrid inviability in Xenopus

“…Embryo nuclei were prepared as previously described 29 from X. tropicalis , l e × t s hybrid, and X. laevis embryos. Briefly, embryos were arrested at stage 8 in late interphase using 150 μg/mL cycloheximide in 1/10X MMR for 60 min.…”

Cell Biology of the Caenorhabditis elegans Nucleus

“…First, during interphase, the nucleus grows in size (see, for example, Cowan and Hyman 2006;Meyerzon et al 2009b). Several studies have shown that the increase in nuclear size is dependent on nuclear import of certain nuclear components, including lamin proteins (Levy and Heald 2010;Jevtic et al 2015). Moreover, nuclear size scales with cell size but the mechanism behind this process is poorly understood (Vukovic et al 2016).…”

A dominant-negative form of POM121 binds chromatin and disrupts the two separate modes of nuclear pore assembly

“…Journal of Cell Science namely importin-a, which is responsible for the rate of import of lamin B3 (Levy and Heald, 2010). To investigate whether the observed block in NE expansion was due to perturbation of the importin-a/b pathway, we tested the effect of the mutated POM121 DN* fragment on pre-assembled nuclei (Fig.…”