Editing Cell nucleus (section)

===Nuclear lamina===
{{Main|Nuclear lamina}}
In animal cells, two networks of [[intermediate filaments]] provide the nucleus with mechanical support: The [[nuclear lamina]] forms an organized meshwork on the internal face of the envelope, while less organized support is provided on the cytosolic face of the envelope. Both systems provide structural support for the nuclear envelope and anchoring sites for chromosomes and nuclear pores.<ref name="MBoC">{{cite book | year = 2002 | title = Molecular Biology of the Cell | chapter = Chapter 4: DNA and Chromosomes | pages = 191–234 | veditors = Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P | location = New York | publisher = Garland Science | edition = 4th | isbn = 978-0-8153-4072-0 }}</ref>

The nuclear lamina is composed mostly of [[lamin]] proteins. Like all proteins, lamins are synthesized in the cytoplasm and later transported to the nucleus interior, where they are assembled before being incorporated into the existing network of nuclear lamina.<ref name="Sturrman">{{cite journal | vauthors = Stuurman N, Heins S, Aebi U | title = Nuclear lamins: their structure, assembly, and interactions | journal = Journal of Structural Biology | volume = 122 | issue = 1–2 | pages = 42–66 | year = 1998 | pmid = 9724605 | doi = 10.1006/jsbi.1998.3987 | department = Review }}</ref><ref name="Goldman">{{cite journal | vauthors = Goldman AE, Moir RD, Montag-Lowy M, Stewart M, Goldman RD | title = Pathway of incorporation of microinjected lamin A into the nuclear envelope | journal = The Journal of Cell Biology | volume = 119 | issue = 4 | pages = 725–35 | date = November 1992 | pmid = 1429833 | pmc = 2289687 | doi = 10.1083/jcb.119.4.725 | department = Primary }}</ref> Lamins found on the cytosolic face of the membrane, such as [[emerin]] and [[nesprin]], bind to the cytoskeleton to provide structural support. Lamins are also found inside the nucleoplasm where they form another regular structure, known as the ''nucleoplasmic veil'',<ref name="RGoldman">{{cite journal | vauthors = Goldman RD, Gruenbaum Y, Moir RD, Shumaker DK, Spann TP | title = Nuclear lamins: building blocks of nuclear architecture | journal = Genes & Development | volume = 16 | issue = 5 | pages = 533–47 | date = March 2002 | pmid = 11877373 | doi = 10.1101/gad.960502 | doi-access = free | department = Review }}</ref><ref name="Broers_2004">{{cite journal | vauthors = Broers JL, Ramaekers FC | title = Dynamics of nuclear lamina assembly and disassembly | journal = Symposia of the Society for Experimental Biology | issue = 56 | pages = 177–92 | date = 2004 | pmid = 15565881 | isbn = 9781134279838 | url = https://books.google.com/books?id=lpR5AgAAQBAJ&pg=PA189 | department = Review }}</ref> that is visible using [[fluorescence microscopy]]. The actual function of the veil is not clear, although it is excluded from the nucleolus and is present during [[interphase]].<ref name="Moir">{{cite journal | vauthors = Moir RD, Yoon M, Khuon S, Goldman RD | title = Nuclear lamins A and B1: different pathways of assembly during nuclear envelope formation in living cells | journal = The Journal of Cell Biology | volume = 151 | issue = 6 | pages = 1155–68 | date = December 2000 | pmid = 11121432 | pmc = 2190592 | doi = 10.1083/jcb.151.6.1155 | department = Primary }}</ref> Lamin structures that make up the veil, such as [[LEM domain-containing protein 3|LEM3]], bind chromatin and disrupting their structure inhibits transcription of protein-coding genes.<ref name="Spann">{{cite journal | vauthors = Spann TP, Goldman AE, Wang C, Huang S, Goldman RD | title = Alteration of nuclear lamin organization inhibits RNA polymerase II-dependent transcription | journal = The Journal of Cell Biology | volume = 156 | issue = 4 | pages = 603–8 | date = February 2002 | pmid = 11854306 | pmc = 2174089 | doi = 10.1083/jcb.200112047 | department = Primary }}</ref>

Like the components of other intermediate filaments, the lamin [[monomer]] contains an [[alpha-helix|alpha-helical]] domain used by two monomers to coil around each other, forming a [[protein dimer|dimer]] structure called a [[coiled coil]]. Two of these dimer structures then join side by side, in an [[Antiparallel (biochemistry)|antiparallel]] arrangement, to form a [[tetramer protein|tetramer]] called a ''protofilament''. Eight of these protofilaments form a lateral arrangement that is twisted to form a ropelike ''filament''. These filaments can be assembled or disassembled in a dynamic manner, meaning that changes in the length of the filament depend on the competing rates of filament addition and removal.<ref name="MBoC" />

Mutations in lamin genes leading to defects in filament assembly cause a group of rare genetic disorders known as ''[[laminopathies]]''. The most notable laminopathy is the family of diseases known as [[progeria]], which causes the appearance of premature [[aging]] in those with the condition. The exact mechanism by which the associated [[biochemistry|biochemical]] changes give rise to the aged [[phenotype]] is not well understood.<ref name="Mounkes">{{cite journal | vauthors = Mounkes LC, Stewart CL | title = Aging and nuclear organization: lamins and progeria | journal = Current Opinion in Cell Biology | volume = 16 | issue = 3 | pages = 322–7 | date = June 2004 | pmid = 15145358 | doi = 10.1016/j.ceb.2004.03.009 | url = https://zenodo.org/record/1258830 | department = Review }}</ref>