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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.
The nuclear envelope is made up of two lipid bilayer membranes, an inner nuclear membrane and an outer nuclear membrane. These membranes are connected to each other by nuclear pores. Two sets of intermediate filaments provide support for the nuclear envelope. An internal network forms the nuclear lamina on the inner nuclear membrane. [7]
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.
The nuclear envelope's structure is determined by a network of intermediate filaments (protein filaments). This network is organized into a mesh-like lining called the nuclear lamina , which binds to chromatin , integral membrane proteins, and other nuclear components along the inner surface of the nucleus.
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.
There was not really a concrete definition of an "intermediate filament protein", in the sense that the size or shape-based definition does not cover a monophyletic group. With the inclusion of unusual proteins like the network-forming beaded lamins (type VI), the current classification is moving to a clade containing nuclear lamin and its many ...
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.
Nucleoporins are a family of proteins which are the constituent building blocks of the nuclear pore complex (NPC). [1] The nuclear pore complex is a massive structure embedded in the nuclear envelope at sites where the inner and outer nuclear membranes fuse, forming a gateway that regulates the flow of macromolecules between the cell nucleus and the cytoplasm.