Question

Based on recent research, what are the structural features of a mitotic chromosome?

Answer 1

Mitotic chromosomes have four structural/functional domains:

centromeres, telomeres, the periphery, and arm chromatin.

Each domain has a characteristic protein composition.

The centromere and its associated kinetochore together comprise an elaborate structure, with over 120 constituents described to date. They bind spindle microtubules and direct chromosome segregation in mitosis.

The protein composition of telomeres is relatively simpler .Telomeres play an essential role in protecting chromosome ends and preventing chromosome fusion events.

The chromosome periphery (perichromosomal layer) may act like a skin protecting the chromosome surface . Its components are enriched in ribosomal and nucleolar proteins. Many may simply be ‘hitchhikers’—proteins that bind to chromosomes in the cytoplasm following nuclear envelope breakdown and serve no essential function during mitosis. Others appear to function during chromosome segregation.

Currently we are using engineered chromosome regions as to provide more detailed information on how DNA is folded within mitotic chromosomes, probing aspects such as the reproducibility of chromatin folding within metaphase chromosomes. We this information as providing valuable constraints and tests for any model for chromosome condensation. We are also initiating a closer structural focus on the dynamics and organization of chromosomal proteins such as condensins during the process of mitotic chromosome condensation.