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Nuclear Lamins, also known as Class V intermediate filaments, are fibrous protein
Fibrous protein

Scleroproteins are one of the two main classes of protein tertiary structure .They are also called fibrous proteins....
s providing structural function and transcriptional regulation in the cell nucleus
Cell nucleus

In cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in all eukaryote cell ....
. Nuclear lamins interact with membrane-associated proteins to form the nuclear lamina
Nuclear lamina

The nuclear lamina is a dense fibrillar network inside the Cell nucleus of an eukaryotic cell. It is composed of intermediate filaments and membrane associated proteins....
 on the interior of the nuclear envelope. They are involved in the breakdown and reformation of the nuclear envelope during mitosis, as well as the positioning of nuclear pores.

etazoan cells there are A and B type lamins which differ in their length and pI
Isoelectric point

The isoelectric point , sometimes abbreviated to IEP, is the pH at which a particular molecule or surface carries no net electric charge....
.






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Nuclear Lamins, also known as Class V intermediate filaments, are fibrous protein
Fibrous protein

Scleroproteins are one of the two main classes of protein tertiary structure .They are also called fibrous proteins....
s providing structural function and transcriptional regulation in the cell nucleus
Cell nucleus

In cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in all eukaryote cell ....
. Nuclear lamins interact with membrane-associated proteins to form the nuclear lamina
Nuclear lamina

The nuclear lamina is a dense fibrillar network inside the Cell nucleus of an eukaryotic cell. It is composed of intermediate filaments and membrane associated proteins....
 on the interior of the nuclear envelope. They are involved in the breakdown and reformation of the nuclear envelope during mitosis, as well as the positioning of nuclear pores.

A, B, and C types

In metazoan cells there are A and B type lamins which differ in their length and pI
Isoelectric point

The isoelectric point , sometimes abbreviated to IEP, is the pH at which a particular molecule or surface carries no net electric charge....
. Human cells have three differentially regulated gene
Gene

A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cell and pass genetic trait to offspring....
s.

  • B-type lamins are present in every cell. B type lamins, B1 and B2, are expressed from the LMNB1
    LMNB1

    Lamin B1, also known as LMNB1, is a human gene.See also* Lamin BReferencesFurther reading...
     and LMNB2 genes on 5q23 and 19q13, respectively.
  • A-type lamins are only expressed following gastrulation
    Gastrulation

    Gastrulation is a phase early in the development of animal embryos, during which the morphology of the embryo is dramatically restructured by cell migration....
    . Lamin A and C are the most common A-type lamins and are splice variants of the LMNA
    LMNA

    Lamin A/C also known as LMNA is a protein which in humans is encoded by the LMNA gene. Lamin A/C belongs to the lamin family of proteins....
     gene found at 1q21.
  • C-type lamins are also subject to tissue subject expression.


Function and structure

These proteins localize to two regions of the nuclear compartment
Cell nucleus

In cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in all eukaryote cell ....
, the nuclear lamina
Nuclear lamina

The nuclear lamina is a dense fibrillar network inside the Cell nucleus of an eukaryotic cell. It is composed of intermediate filaments and membrane associated proteins....
 -- a proteinaceous structure layer subjacent to the inner surface of the nuclear envelope
Nuclear envelope

The nuclear envelope is a double lipid bilayer that encloses the genetic material in eukaryote cell . The nuclear envelope also serves as the physical barrier, separating the contents of the nucleus from the cytosol ....
 and throughout the nucleoplasm in the nucleoplasmic "veil".

Comparison of the lamins to cytoskeletal intermediate filaments shows that lamins have an extra 42 residues (six heptads) within coil 1b. The c-terminal tail domain contains a nuclear localization signal
Nuclear localization signal

A nuclear localization signal or sequence is an amino acid sequence which acts like a 'tag' on the exposed surface of a protein. This sequence is used to target the protein to the cell nucleus through the Nuclear Pore Complex and to direct a newly synthesized protein into the nucleus via its recognition by cytosolic nuclear transpo...
 (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.

Lamin A and lamin C form homodimers which associate head to tail.

During mitosis, lamins are phosphorylated by Mitosis Promoting Factor (MPF) which drives the disassembly of the lamina and the nuclear envelope. After chromosome segregation, dephosphorylation of nuclear lamins promotes reassembly of the nuclear envelope.

See also

  • intermediate filament
    Intermediate filament

    Intermediate filaments are a family of related proteins that share common structural and sequence features. Intermediate filaments have an average diameter of 10 nanometers, which is between that of actin and microtubules, although they were initially designated 'intermediate' because their average diameter was between those of narrower mi...
  • nuclear lamina
    Nuclear lamina

    The nuclear lamina is a dense fibrillar network inside the Cell nucleus of an eukaryotic cell. It is composed of intermediate filaments and membrane associated proteins....
  • laminopathies


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