The Role of the RanGTPase in Mitotic Spindle Assembly

Abstract

Mitosis is the process whereby a cell separates its paired chromosomes into two new identical daughter cells. To achieve this and maintain the correct amount of deoxyribo nuclic acid (DNA) in the cells, the cell forms a framework called the mitotic spindle onto which the chromosomes attach and then get pulled into the new daughter cells. The mitotic spindle is made up of microtubules and associated proteins. The GTPase Ran, which is important for nuclear import and export, plays important roles in regulating the formation of the mitotic spindle. Ran can bind and hydrolyse guanosine triphosphate (GTP), which enables it to regulate several cellular processes. Generation of Ran‐GTP at the chromosomes creates an intracellular gradient that provides directionality to nuclear cytoplasmic transport during interphase and creates an environment around the chromosomes to facilitate spindle assembly. Key Concepts: Ran is a small GTPase. During interphase, spindle assembly factors bind to Importin‐β and are transported into the nucleus. Ran‐GTP is generated at chromosomes and releases spindle assembly factors from inhibitory binding to Importin‐β. Gradients of Ran‐GTP and released cargo proteins are generated in mitotic cells that are important for regulating many activities.

The SelfishSegregation DistorterGene Complex ofDrosophila melanogaster

“…Ran is involved in mitotic spindle assembly, nuclear envelope assembly, chromosome segregation, and processes occurring during anaphase and cytokinesis (Joseph et al 2002;reviewed in Quimby and Dasso 2003;Renshaw and Wilde 2011;Figure 8). RanGAP and RanGEF are critical in establishing the gradient of Ran-GDP and Ran-GTP for these other cellular functions and not only across the nuclear envelope ( Figure 8A).…”