CEN function

The centromere, through interaction with the kinetochore, is important for chromosome movement.

The mitotic spindle, to which chromosomes become attached during mitosis, consists of microtubules emanating from a MTOC (microtubule organizing center: centrosome or spindle polar body). In some organisms, the microtubules grow from the centrosome. In others, they originate from the kinetochore. The former have been more extensively studied.
Microtubules are long fibers built by polymerization of alpha- and beta- tubulin dimers. Their polymerization is inhibited by colchicine. Gamma-tubulin is found in MTOC's and may nucleate tubulin polymerization.
S. cerevisiae CEN DNA was added to microbeads. Protein CBF3 from S.cerevisiae was added to the DNA beads. The beads were placed on a microscope slide containing surface-attached microtubules.
The microbeads moved in one direction along the microtubules when ATP was supplied. Such movement is typical of cytoplasmic streaming and other movements of subcellular components. These are known to involve protein motors, either dynein or kinesin.
Artificial chromosomes containing centromeres with assembled kinetochores also glide along slide-fixed microtubules. The movement is sensitive to inhibitors that inhibit the dynein motor.
Antibodies against dynein recognize a protein in kinetochores.

Movement of chromosomes during segregation is due to dynein-like protein motors acting on microtubule tracks, where the motors are attached to chromosomes at CEN sequences.

The role of motors in segregation of chromosomes is under investigation.
Motors may also segregate chromosomes by pushing apart the spindle pole bodies. This occurs when a motor complex is attached to a pair of microtubules not attached to centromeres, one microtubule from each spindle pole body.
Segregation is followed by cytokinesis.
Fluorescent stains allow visualization of the process in live nuclei.

E-mail inquiries to U. Melcher------------Last Updated: 31 August, 2005