Cellular memory modules: Difference between revisions

Revision as of 01:25, 24 April 2023

Revision as of 15:15, 12 August 2023

Line 1:

'''Cellular memory modules''' are a form of [[Transgenerational epigenetic inheritance|epigenetic inheritance]] that allow cells to maintain their original identity after a series of [[Cell division|cell divisions]] and developmental processes. Cellular memory modules implement these preserved characteristics into transferred environments through [[transcriptional memory]].<ref>{{Citation |last=Paro |first=Renato |title=Cellular Memory |date=2021 |url=https://doi.org/10.1007/978-3-030-68670-3_3 |work=Introduction to Epigenetics |pages=49–66 |editor-last=Paro |editor-first=Renato |access-date=2023-04-20 |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-68670-3_3 |isbn=978-3-030-68670-3 |last2=Grossniklaus |first2=Ueli |last3=Santoro |first3=Raffaella |last4=Wutz |first4=Anton |editor2-last=Grossniklaus |editor2-first=Ueli |editor3-last=Santoro |editor3-first=Raffaella |editor4-last=Wutz |editor4-first=Anton|doi-access=free }}</ref> Cellular memory modules are primarily found in ''[[Drosophila]]''.

== History ==

Line 6:

== Locations and mechanisms: experiment overviews ==

[[File:Cell_memory_modules.jpg|thumb|PcG proteins repress transcription in salivary glands. A shows an active transcription. B shows transcription after addition of a promoter. C shows transcription of a mutant protein. D shows transcription become depressed.]]

Cellular memory modules have the same general process of genes undergoing [[Transcription (biology)|transcription]], these genes being transferred to an unfamiliar environment, and then these genes reverting to their original characteristics preserved through transcriptional memory. Cellular memory modules preserve repressed and active [[chromatin]] states in the [[Polycomb-group proteins|Polycomb group (PcG)]] and [[Trithorax-group proteins|trithorax group (trxG)]] proteins by using Polycomb- and trithorax [[response element]]s, which are just DNA sequences.<ref name="Déjardin-2004">{{Cite journal |last=Déjardin |first=Jérôme |last2=Cavalli |first2=Giacomo |date=2004-02-25 |title=Chromatin inheritance upon Zeste-mediated Brahma recruitment at a minimal cellular memory module |url=http://emboj.embopress.org/cgi/doi/10.1038/sj.emboj.7600108 |journal=The EMBO Journal |volume=23 |issue=4 |pages=857–868 |doi=10.1038/sj.emboj.7600108 |issn=0261-4189 |pmc=381013 |pmid=14963490}}</ref> Transcription resets and alters [[Epigenetic marker|epigenetic marks]] on chromosomal memory elements that are regulated by PcG and trxG proteins.<ref>{{Cite journal |last=Rank |first=Gerhard |last2=Prestel |first2=Matthias |last3=Paro |first3=Renato |date=2002-11-01 |title=Transcription through Intergenic Chromosomal Memory Elements of the Drosophila Bithorax Complex Correlates with an Epigenetic Switch |url=https://doi.org/10.1128/MCB.22.22.8026-8034.2002 |journal=Molecular and Cellular Biology |volume=22 |issue=22 |pages=8026–8034 |doi=10.1128/MCB.22.22.8026-8034.2002 |pmid=12391168|pmc=134728 }}</ref> PcG genes maintain silent expression states during the development of [[Hox gene|Hox genes]] while trxG proteins maintain Hox gene expression patterns. PcG proteins bind to Polycomb response elements (PREs) to repress the target gene and silence their transcription<ref>{{Cite journal |last=Bantignies |first=Frédéric |last2=Cavalli |first2=Giacomo |date=2006-06-01 |title=Cellular memory and dynamic regulation of polycomb group proteins |url=https://www.sciencedirect.com/science/article/pii/S0955067406000536 |journal=Current Opinion in Cell Biology |series=Nucleus and gene expression |language=en |volume=18 |issue=3 |pages=275–283 |doi=10.1016/j.ceb.2006.04.003 |issn=0955-0674}}</ref> by excluding [[transcriptional activators]] and making the gene unable to undergo RNA synthesis.<ref>{{Cite journal |last=Orlando |first=Valerio |date=2003-03-07 |title=Polycomb, Epigenomes, and Control of Cell Identity |url=https://www.cell.com/cell/abstract/S0092-8674(03)00157-0 |journal=Cell |language=English |volume=112 |issue=5 |pages=599–606 |doi=10.1016/S0092-8674(03)00157-0 |issn=0092-8674 |pmid=12628181|doi-access=free }}</ref> While the basis of the mechanism among cellular memory modules is the same, what initiates the mechanism and the specific proteins carrying it out differ based on the ___location of the cellular memory module within the gene. Some of these specific mechanisms and gene locations have been analyzed from experiments and outlined below.

=== Ab-Fab Mechanism ===

Line 12:

=== H3K27 Mechanism ===

Polycomb repressive complexes (PRC) [[PRC1|1]] and 2 are recruited to bind to the [[H3K27me3]] gene, which is found at the beginning of ''Drosophila'' embryogenesis. [[PRC2]] then catalyzes the gene’s [[DNA methylation|methylation]], inducing PCR2 recruitment and compacting the chromatin. The research found that PRC2 recruitment is dependent on the presence of the H2AKub sequence. However, even after mutations in the H3K27 residue, PcGs were able to be recruited and revert to their original [[Phenotype|phenotypes]] indicating a transcriptional change in the H3K27 residue.<ref>{{Cite journal |last=Marasca |first=Federica |last2=Bodega |first2=Beatrice |last3=Orlando |first3=Valerio |date=April 2018 |title=How Polycomb-Mediated Cell Memory Deals With a Changing Environment: Variations in PcG complexes and proteins assortment convey plasticity to epigenetic regulation as a response to environment |url=https://onlinelibrary.wiley.com/doi/10.1002/bies.201700137 |journal=BioEssays |language=en |volume=40 |issue=4 |pages=1700137 |doi=10.1002/bies.201700137|hdl=10754/627331 |hdl-access=free }}</ref>

== Applications ==