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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]
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] Lamins are present in all animals but are not found in microorganisms, plants or fungi.
The nuclear pore complex (NPC), is a large protein complex giving rise to the nuclear pore. Nuclear pores are found in the nuclear envelope that surrounds the cell nucleus in eukaryotic cells . The nuclear envelope is studded by a great number of nuclear pores that give access to various molecules, to and from the nucleoplasm and the cytoplasm.
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.
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]
Lamin proteins are thought to be involved in nuclear stability, chromatin structure, and gene expression. Vertebrate lamins consist of two types, A and B. This gene encodes one of the two B type proteins, B1. [7] Lamin B, along with heterochromatin, is anchored to the inner surface of the nuclear membrane by the lamin B receptor.
The main components of the nuclear envelope are a double membrane, nuclear pore complexes, and a nuclear lamina internal to the inner nuclear membrane. These components are dismantled during prophase and prometaphase and reconstructed during telophase, when the nuclear envelope reforms on the surface of separated sister chromatids.