Final answer:
Importin's interaction with the protein of the centromeres facilitates the release of proteins that help in the assembly of spindle microtubules, especially during prometaphase of mitosis.
Step-by-step explanation:
Interaction between importin and the protein of the centromeres leads to the release of importin-bound proteins that promote spindle microtubule assembly. During prometaphase, a significant phase in mitosis, the nuclear envelope breaks down and allows the mitotic spindle, composed of microtubules, to attach to chromosomes via the kinetochores located on the centromeres. It's crucial to note that there are different types of spindle microtubules, such as polar microtubules and kinetochore microtubules. Polar microtubules, which extend from centrioles or MTOCs, overlap and contribute to the elongation of the cell, while kinetochore microtubules attach to the kinetochores and play a vital role in chromosome segregation.