Genome complexity: epigentic coding for cell division (Introduction)

by David Turell @, Friday, September 09, 2016, 00:02 (2759 days ago) @ David Turell

Scientists have found out how epigenetic tags on DNA are carried forward into new cells:-https://www.sciencedaily.com/releases/2016/09/160907160525.htm-"Epigenetic tags help tell genes -- stretches of DNA that act as biological instruction manuals -- when to switch "on" and "off," ultimately determining cell type and function. DNA methylation, or the addition of methyl tags to DNA, is one of the most well-studied epigenetic signals; errors in this process are commonly found in cancer.-***- "The findings center on a protein called UHRF1, a guardian of the cell's epigenetic information that can recognize patterns of epigenetic tags and promote the addition of new ones. These "reading" and "writing" activities of UHRF1 are well understood on their own but until now, scientists didn't know exactly how or even if these UHRF1 activities worked together.-***-"Here's what they found -- during cell division, UHRF1 recognizes newly copied DNA at sites that are missing methyl tags. At the same time, it also recognizes a protein associated with DNA called histone H3 and attaches another small protein called ubiquitin on that histone. This ubiquitin protein acts as a molecular flag, signaling to another protein called a DNA methylation enzyme that a methyl tag is needed there. The group discovered that ubiquitin attachment on the histone is promoted by the pre-existing pattern of epigenetic signals recognized by UHRF1. This is the first time an epigenetic signal has been shown to impact ubiquitylation and connects the patterns of epigenetic information in a new way.-"'While the functions of the individual parts of UHRF1 were already known, we didn't appreciate the interdependence of these functions in adding ubiquitin to histones," said Joe Harrison, Ph.D., a postdoctoral fellow in the Kuhlman Laboratory at UNC and the paper's first author. "This exquisite regulation of an ubiquitin ligase has not been previously described and is very exciting for the field of ubiqutin biology.'"-Comment: Once again we see amazing complexity of how a molecule can act to preserve or change DNA by watching DNA methylation flagging. Unless one thinks molecules do this intelligently through their own thought, this is done automatically.


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