Exposure of zebrafish nuclei to meiotic cytosol resulted in phosphorylation of NEP55 and L68 proteins by cyclin-dependent kinase 2. NEP55 is a protein of the inner nuclear membrane, and L68 is a protein of the nuclear lamina. What is the most likely role of phosphorylation of these proteins in the process of mitosis?
A) They enable the attachment of the spindle microtubules to kinetochore regions of the centromere.
B) They are involved in the disassembly and dispersal of the nucleolus.
C) They are involved in the disassembly of the nuclear envelope.
D) They assist in the movement of the centrosomes to opposite sides of the nucleus.

Question

Quizplus · Accepted Answer

The phosphorylation of NEP55 and L68, both components of the nuclear envelope, suggests their involvement in the disassembly of the nuclear envelope, which is a hallmark of the transition from interphase to mitosis. The breakdown of the nuclear envelope is necessary for the spindle microtubules to access the chromosomes and for the segregation of genetic material during mitosis. Therefore, C is the most suitable choice. A is incorrect since it concerns kinetochore protein phosphorylation. B refers to nucleolus disassembly, which happens during prophase, but is not linked to phosphorylation of these specific proteins. D relates to centrosome movement and cytokinesis and it does not seem directly relevant to phosphorylation of these proteins.

Exposure of Zebrafish Nuclei to Meiotic Cytosol Resulted in Phosphorylation