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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.
Nuclear lamins interact with inner nuclear membrane proteins to form the nuclear lamina on the interior of the nuclear envelope. Lamins have elastic and mechanosensitive properties, and can alter gene regulation in a feedback response to mechanical cues. [ 1 ]
The nuclear lamina consist of a two-dimensional matrix of proteins located next to the inner nuclear membrane. The lamin family of proteins make up the matrix and are highly conserved in evolution. During mitosis , the lamina matrix is reversibly disassembled as the lamin proteins are phosphorylated .
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]
This made it possible to test if laminins could have a significant role in vitro as they have in the human body. In 2008, two groups independently showed that mouse embryonic stem cells can be grown for months on top of recombinant laminin-511.
Laminopathies (lamino-+ -pathy) are a group of rare genetic disorders caused by mutations in genes encoding proteins of the nuclear lamina.Since the first reports of laminopathies in the late 1990s, increased research efforts have started to uncover the vital role of nuclear envelope proteins in cell and tissue integrity in animals.
The c-terminal tail domain contains a nuclear localization signal (NLS), an Ig-fold-like domain, and in most cases a carboxy-terminal CaaX box that is isoprenylated and carboxymethylated (lamin C does not have a CAAX box). Lamin A is further processed to remove the last 15 amino acids and its farnesylated cysteine.
In contrast to the cytoskeleton, however, the nuclear matrix has been proposed to be a dynamic structure. Along with the nuclear lamina, it supposedly aids in organizing the genetic information within the cell. [1] The exact function of this structure is still disputed, and its very existence has been called into question. [2]