Editing Cell nucleus (section)

====Paraspeckles====
{{Main|Paraspeckle}}
Discovered by Fox et al. in 2002, paraspeckles are irregularly shaped compartments in the interchromatin space of the nucleus.<ref name="Fox_2010">{{cite journal | vauthors = Fox AH, Lamond AI | title = Paraspeckles | journal = Cold Spring Harbor Perspectives in Biology | volume = 2 | issue = 7 | pages = a000687 | date = July 2010 | pmid = 20573717 | pmc = 2890200 | doi = 10.1101/cshperspect.a000687 | department = Review }}</ref>  First documented in HeLa cells, where there are generally 10–30 per nucleus,<ref name="para2">{{cite web | last1 =Fox | first1 =Archa | first2 = Wendy | last2 = Bickmore | name-list-style = vanc | title = Nuclear Compartments: Paraspeckles | publisher = Nuclear Protein Database | year = 2004 | url =http://npd.hgu.mrc.ac.uk/compartments/paraspeckles.html | archive-url = http://webarchive.nationalarchives.gov.uk/20080910110920/http://npd.hgu.mrc.ac.uk/compartments/paraspeckles.html | url-status =dead | archive-date =10 September 2008 | access-date = 6 March 2007 }}</ref> paraspeckles are now known to also exist in all human primary cells, transformed cell lines, and tissue sections.<ref name="para3">{{cite journal | vauthors = Fox AH, Bond CS, Lamond AI | title = P54nrb forms a heterodimer with PSP1 that localizes to paraspeckles in an RNA-dependent manner | journal = Molecular Biology of the Cell | volume = 16 | issue = 11 | pages = 5304–15 | date = November 2005 | pmid = 16148043 | pmc = 1266428 | doi = 10.1091/mbc.E05-06-0587 | department = Primary }}</ref> Their name is derived from their distribution in the nucleus; the "para" is short for parallel and the "speckles" refers to the splicing speckles to which they are always in close proximity.<ref name="para2"/>

Paraspeckles sequester nuclear proteins and RNA and thus appear to function as a molecular sponge<ref name="Nakagawa_2018">{{cite journal | vauthors = Nakagawa S, Yamazaki T, Hirose T | title = Molecular dissection of nuclear paraspeckles: towards understanding the emerging world of the RNP milieu | journal = Open Biology | volume = 8 | issue = 10 | date = October 2018 | page = 180150 | pmid = 30355755 | pmc = 6223218 | doi = 10.1098/rsob.180150 | department = Review }}</ref> that is involved in the regulation of gene expression.<ref name="Pisani_2019">{{cite journal | vauthors = Pisani G, Baron B | title = Nuclear paraspeckles function in mediating gene regulatory and apoptotic pathways | journal = Non-Coding RNA Research | volume = 4 | issue = 4 | pages = 128–134 | date = December 2019 | pmid = 32072080 | pmc = 7012776 | doi = 10.1016/j.ncrna.2019.11.002 | department = Review }}</ref> Furthermore, paraspeckles are dynamic structures that are altered in response to changes in cellular metabolic activity. They are transcription dependent<ref name="Fox_2010" /> and in the absence of RNA Pol II transcription, the paraspeckle disappears and all of its associated protein components  (PSP1, p54nrb, PSP2, CFI(m)68, and PSF) form a crescent shaped perinucleolar cap in the nucleolus. This phenomenon is demonstrated during the cell cycle. In the [[cell cycle]], paraspeckles are present during [[interphase]] and during all of [[mitosis]] except for [[telophase]]. During telophase, when the two daughter nuclei are formed, there is no [[RNA]] Pol II [[Transcription (genetics)|transcription]] so the protein components instead form a perinucleolar cap.<ref name="para3"/>