Spindle pole body

Spindle pole body (SPB) is a structure found in the cells of fungi, which is functionally equivalent to the centrosome in animal cells. The SPB is crucial for mitosis and meiosis, as it is responsible for the organization and segregation of chromosomes.

Structure

The SPB is a multi-layered structure composed of several proteins. The central layer, known as the central plaque, is embedded in the nuclear envelope. The inner and outer plaques are located on the nucleoplasmic and cytoplasmic sides of the envelope, respectively. The outer plaque serves as a nucleation site for microtubules, which are essential for chromosome segregation.

Function

The primary function of the SPB is to organize the microtubule cytoskeleton during cell division. It duplicates and separates to form the two poles of the mitotic spindle. The SPB also plays a role in other cellular processes, such as nuclear migration and cell polarity.

Role in Cell Division

During cell division, the SPB duplicates and migrates to opposite ends of the nucleus. This process is regulated by a variety of proteins, including Cdc31, Spc42, and Spc110. These proteins ensure that the SPB duplicates once and only once per cell cycle, and that the duplicated SPBs separate correctly.

Role in Disease

Mutations in SPB components can lead to defects in cell division, which can contribute to diseases such as cancer. For example, mutations in the gene encoding the SPB component Spc98 have been linked to certain types of leukemia.

See Also

• Centrosome
• Mitosis
• Meiosis
• Microtubule