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The nuclear envelope, also known as the nuclear membrane, [1] [a] is made up of two lipid bilayer membranes that in eukaryotic cells surround the nucleus, which encloses the genetic material. The nuclear envelope consists of two lipid bilayer membranes: an inner nuclear membrane and an outer nuclear membrane. [ 4 ]
The phosphorylation of the protein targets of M-Cdks (Mitotic Cyclin-dependent Kinases) drives spindle assembly, chromosome condensation and nuclear envelope breakdown in early mitosis. The dephosphorylation of these same substrates drives spindle disassembly, chromosome decondensation and the reformation of daughter nuclei in telophase.
The nuclear lamina consists of two components, lamins and nuclear lamin-associated membrane proteins. The lamins are type V intermediate filaments which can be categorized as either A-type (lamin A, C) or B-type (lamin B 1, B 2) according to homology of their DNA sequences, biochemical properties and cellular localization during the cell cycle.
In most cells, the disassembly of the nuclear envelope marks the end of the prophase of mitosis. However, this disassembly of the nucleus is not a universal feature of mitosis and does not occur in all cells. Some unicellular eukaryotes (e.g., yeasts) undergo so-called closed mitosis, in which the nuclear envelope remains intact. In closed ...
During mitosis, lamins are phosphorylated by Mitosis-Promoting Factor (MPF), which drives the disassembly of the lamina and the nuclear envelope. This allows chromatin to condense and the DNA to be replicated. After chromosome segregation, dephosphorylation of nuclear lamins by a phosphatase promotes reassembly of the nuclear envelope.
Depolymerization of the nuclear lamins leads to disintegration of the nuclear envelope. Transfection experiments demonstrate that phosphorylation of human lamin A is required for lamin depolymerization, and thus for disassembly of the nuclear envelope, which normally occurs early in mitosis.
A nuclear pore is a channel as part of the nuclear pore complex (NPC), a large protein complex found in the nuclear envelope of eukaryotic cells.The nuclear envelope (NE) surrounds the cell nucleus containing DNA and facilitates the selective membrane transport of various molecules.
During eukaryotic mitosis the nuclear envelope disintegrates into vesicles dispersing nuclear lamina proteins and nuclear pore complexes.Nup210 is specifically phosphorylated on the C-terminal (cytoplasmic) domain in mitosis at Ser1880 [7] and is dispersed throughout the endoplasmic reticulum during mitosis as homodimers. [8]