Editing Nucleoplasm (section)

== Composition ==
The nucleoplasm is a highly viscous liquid that is enveloped by the nuclear membrane and consists mainly of water, proteins, dissolved ions, and a variety of other substances including nucleic acids and minerals.

=== Proteins ===
There are around 20,000 [[protein-coding genes]] in humans,<ref name="Genome">{{cite web |title=Gene |url=https://www.genome.gov/genetics-glossary/Gene#:~:text=And%20genes%20are%20the%20part,of%20the%20entire%20human%20genome. |website=www.genome.gov |access-date=7 January 2025 |language=en}}</ref> and nearly a third of these have been found to  localize to the nucleoplasm via targeting by a [[nuclear localization sequence]] (NLS).<ref name="proteinatlas_nucleoplasm"/> Cytosolic proteins, known as [[importin]]s, act as receptors for the NLS, escorting the protein to a nuclear pore complex to be transported into the nucleoplasm.<ref name=":3">{{cite book |last=Casem|first=Merri Lynn|date=2016 |title=Case Studies in Cell Biology |publisher=Elsevier|pages=73–103 |isbn=978-0-12-801394-6}}</ref> Proteins in the nucleoplasm are mainly tasked with participating in and regulating cellular functions that are DNA-dependent, including transcription, [[RNA splicing]], [[DNA repair]], [[DNA replication]], and a variety of metabolic processes.<ref name="proteinatlas_nucleoplasm"/> These proteins are divided into histone proteins, a class of proteins that bind to DNA and give chromosomes their shape and regulate gene activity,<ref>{{cite journal |last1=Stein |last2=Thrall |first2=C.L. |date=1973|title=Evidence for the presence of nonhistone chromosomal proteins in the nucleoplasm of HeLa S3 cells |journal=FEBS Letters |volume=32 |issue=1 |pages=41–45 |doi=10.1016/0014-5793(73)80732-X|pmid=4715686 |s2cid=20285491 |doi-access=free }}</ref> and non-histone proteins.

The nucleoplasm contains many enzymes that are instrumental in the synthesis of DNA and RNA, including [[DNA polymerase]] and [[RNA polymerase]] which function in DNA replication and RNA transcription, respectively. Additionally, the nucleoplasm is host to many of the enzymes that play essential roles in [[cellular metabolism]]. [[NAD+ synthase]] is stored in the nucleoplasm and functions in electron transport and [[redox reaction]]s involved with the [[electron transport chain]] and synthesis of [[adenosine triphosphate]] (ATP).<ref>{{cite journal |last1= Houtkooper |last2= Cantó |first2=C. |last3=Wanders |first3=R.J. |last4= Auwerx |first4=J. |date=2010|title=The Secret Life of NAD+: An Old Metabolite Controlling New Metabolic Signaling Pathways |journal= Endocrine Reviews|volume=31 |issue=2 |pages=194–223 |doi=10.1210/er.2009-0026|pmid= 20007326 |pmc= 2852209 }}</ref> [[Pyruvate kinase]] is also found in the nucleoplasm in significant quantities; this enzyme is involved in the final step of [[glycolysis]], catalyzing the conversion of [[phosphoenolpyruvate]] (PEP) to [[pyruvate]] along with the phosphorylation of [[adenosine diphosphate]] (ADP) to ATP.<ref>{{cite journal |last1= Israelsen |last2= Vander Heiden |first2=M.G. |date=2015|title=Pyruvate kinase: Function, regulation and role in cancer |journal=Seminars in Cell & Developmental Biology |volume=43 |pages=43–51 |doi=10.1016/j.semcdb.2015.08.004|pmid= 26277545 |pmc= 4662905 }}</ref> Importantly, the nucleoplasm contains [[Cofactor (biochemistry)|co-factor]]s and co-enzymes, including [[acetyl-CoA]], which plays a vital role in the [[citric acid cycle]],<ref>{{cite journal |last1=Falcón |last2=Chen |first2=S. |last3=Wood |first3=M.S. |last4=Aris |first4=J.P.|date=2010 |title=Acetyl-coenzyme A synthetase 2 is a nuclear protein required for replicative longevity in Saccharomyces cerevisiae |journal=Molecular and Cellular Biochemistry |volume=333 |issue=1–2 |pages=99–108 |doi=10.1007/s11010-009-0209-z|pmid=19618123 |pmc=3618671 }}</ref> and ATP, which is involved in energy storage and transfer.

=== Ions ===
[[File:NaKpompe2.jpg|thumb|alt=alt text|An example of the [[sodium-potassium pump]], a [[P-type ATPase]], which controls the ionic gradient across the [[cell membrane]] and the [[nuclear envelope]] as well as the ionic makeup of the nucleoplasm through the selective pumping of [[sodium]] and [[potassium]] [[ion]]s.]]
The ionic composition of the nucleoplasm is crucial in maintaining [[homeostasis]] within the cell and the organism as a whole. Ions that have been documented in the nucleoplasm include [[sodium]], [[potassium]], [[calcium]], [[phosphorus]], and [[magnesium]]. These ions are key players in a variety of biological functions. Sodium and potassium play key roles in the [[sodium-potassium pump]], a [[transmembrane]] [[ATPase]] that pumps three sodium ions out of the cell for every two potassium ions it pumps into the cell, creating an ionic gradient.<ref>{{cite journal |url=https://pdb101.rcsb.org/motm/118 |title=Molecule of the Month: Sodium-Potassium Pump |last=Goodsell |first=David |date=October 2009 |website=PDB-101 |access-date=October 30, 2022 |doi=10.2210/rcsb_pdb/mom_2009_10|url-access=subscription }}</ref> While this pump is generally considered to be a [[plasma membrane]] protein, its presence has been recorded in the nuclear envelope, controlling the ionic gradient between the cytoplasm and nucleoplasm of the cell and contributing to the homeostasis of calcium within the cell.<ref>{{cite journal |last1=Galva |first1=Charitha |last2=Artigas |first2=Pablo |last3=Gatto |first3=Craig |date= December 2012|title=Nuclear Na+/K+-ATPase plays an active role in nucleoplasmic Ca2+ homeostasis |journal= Journal of Cell Science|volume=125 |issue=24 |pages=6137–6147 |doi=10.1242/jcs.114959|pmid=23077175 |pmc=3585523 }}</ref> These ions also determine the concentration gradient that exists between the cytoplasm and nucleoplasm, serving to control the flow of ions across the nuclear envelope.<ref>{{cite journal |last1=Wu |first1= Yufei |last2=Pegoraro |first2=Adrian |last3=Weitz |first3=David |last4=Janmey |first4=Paul|last5=Sun|first5=Sean|date= February 2022|title=The correlation between cell and nucleus size is explained by an eukaryotic cell growth model |journal= PLOS Computational Biology|volume=18 |issue=2 |pages= e1009400 |doi=10.1371/journal.pcbi.1009400|pmid= 35180215 |pmc= 8893647 |doi-access= free }}</ref> They are important in maintaining the osmolarity of the nucleoplasm which in turn provides structural integrity to the nuclear envelope as well as the organelles suspended in the dense nucleoplasm.