nuclear envelope breaking down

[dfgdfg]

during prophase when the nuclear envelope breaks down, what causes the nuclear envelope to break down?

[JackBean]

I think, it's phosphorylation of cyclin B1-Cdk1 and Cdc25C causing their translocation into nucleus.

[kolean]

from Lodish's Molecular Cell Biology:

MPF-catalyzed phosphorylation of specific nucleoporins causes nuclear pore complexes to dissociate into subcomplexes during prophase. Phosphorylation of integral membrane proteins of the inner nuclear membrane is thought to decrease their affinity for chromatin and further contribute to disassembly of the nuclear envelope. The weakening of the associations between the inner nuclear membrane proteins and the nuclear lamina and chromatin allows sheets of inner nuclear membrane to retract into the endoplastmic reticulum, which is continuous with the outer nuclear membrane.