![]() Many of the chromosome movements in mitosis are governed by the kinetochore fibers (K-fibers) of the spindle apparatus. It requires the correct assembly of a bipolar array of microtubules (MTs) into a mitotic spindle which, in concert with hundreds of different motors and non-motor proteins, segregates the duplicated sister chromatids to the two daughter cells. Further work is needed to identify the other proteins and molecules that make up the mesh.Īccurate mitosis is essential to eukaryotic life. This suggests that cells must maintain optimal levels of TACC3 to ensure that the K-fibers can effectively separate the chromosomes. analyzed how disorganized K-fibers affected dividing cells and found that it took longer for the chromosomes to move to the newly forming daughter cells. ![]() These observations suggest that ‘the mesh’ influences the microtubule spacing within a K-fiber. The spacing of the microtubules with the K-fibers was reduced so that they were more tightly packed than normal. then increased the levels of the TACC3 protein and found that the K-fibers became disorganized. This means that, in a three-dimensional view, the connectors appear as a ‘mesh’ between the microtubules in the bundle. These connectors can vary in size and a single connector can link up to four microtubules. This analysis revealed struts or connectors that hold together adjacent microtubules within K-fibers. Now, Nixon et al.-including several of the researchers involved in the 2011 work-have used a technique called 3D electron tomography to analyze what holds the K-fibers together in human cells. However, it remained unclear how these proteins achieved this. ![]() These bundles of microtubules are held together throughout their entire length and, in 2011, it was suggested that a group of proteins including one called TACC3 could cross-link adjacent microtubules within K-fibers. K-fibers are organized in a way that provides strength. The spindle is made up of a network of long, protein filaments called microtubules, and the bundles of microtubules that attach to the chromosomes are referred to as ‘K-fibers’. In the cells of plants, animals, and fungi, a structure known as the spindle pulls the two copies of the chromosomes apart. Our work thus identifies the K-fiber meshwork of linked multipolar connectors as a key integrator and determinant of K-fiber structure and function.īefore a cell divides, its genetic material must be copied and then equally distributed between the newly formed daughter cells. We propose that the mesh stabilizes K-fibers by pulling MTs together and thereby maintaining the integrity of the fiber. Optimal stabilization of K-fibers by the mesh is required for normal progression through mitosis. Molecular manipulation of the mesh by overexpression of TACC3 causes disorganization of the K-fiber MTs. Each connector has up to four struts, so that a single connector can link up to four MTs. The K-fiber mesh is made of linked multipolar connectors. Here, we show, using 3D electron microscopy, that K-fiber microtubules (MTs) are connected by a network of MT connectors. K-fibers are composed of many microtubules that are held together throughout their length. ![]() Kinetochore fibers (K-fibers) of the mitotic spindle are force-generating units that power chromosome movement during mitosis.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |