Featured Research

from universities, journals, and other organizations

Histone-modifying proteins, not histones, remain associated with DNA through replication

Date:
August 23, 2012
Source:
Thomas Jefferson University
Summary:
A study of Drosophila embryos found that parental methylated histones are not transferred to daughter DNA. Rather, after DNA replication, new nucleosomes are assembled from newly synthesized unmodified histones.

It's widely accepted that molecular mechanisms mediating epigenetics include DNA methylation and histone modifications, but a team from Thomas Jefferson University has evidence to the contrary regarding the role of histone modifications.

Related Articles


A study of Drosophila embryos from Jefferson's Department of Biochemistry and Molecular Biology published ahead of print in Cell August 23 found that parental methylated histones are not transferred to daughter DNA. Rather, after DNA replication, new nucleosomes are assembled from newly synthesized unmodified histones.

"Essentially, all histones are going away during DNA replication and new histones, which are not modified, are coming in," said Alexander M. Mazo, Ph.D., professor of Biochemistry and Molecular Biology at Jefferson, and a member of Jefferson's Kimmel Cancer Center. "In other words, what we found is that histone modifying proteins are hiding on the way over replicating DNA, instead of histones 'jumping' over as currently thought."

"What this paper tells us," he continues, "is that these histone modifying proteins somehow are able to withstand the passage of the DNA replication machinery. They remained seated on their responsive binding sites, and in all likelihood they will re-establish histone modification and finalize the chromatin structure that allows either activation or repression of the target gene."

The team suggests that since it appears these histone modifying proteins -- the Trithorax-group (TrxG), which maintain gene expression, and the Polycomb-group (PcG), which plays a role in epigenetic silencing of genes -- re-establish the histone code on newly assembled unmethylated histones, they may act as epigenetic marks.

Epigenetics is the study of heritable changes in gene expression caused by mechanisms other than changes in the underlying DNA sequence. Epigenetic marks have become an important focus in recent years because they are thought to have the potential to explain mechanisms of aging, human development, and the origins of diseases, like cancer, heart disease, and mental illness.

According to widely-accepted models applied today, the tails of methylated histones turn genes in DNA "on" or "off" by loosening or tightening nucleosome structure, thus changing the accessibility of transcription factors and other proteins to DNA.

"People believe that everything gets worked off of DNA during the replication process and that these methylated histones act as epigenetic marks, since they are believed to rapidly jump from parental to daughter DNA" said Dr. Mazo. "But there is no experimental evidence to back this up."

The researchers used chromatin immunoprecipitation (ChIP) assay, and developed several new approaches to analyze protein interactions with newly synthesized DNA, tracking both modified and unmodified histones, and non-histone proteins to determine their presence and role from the initial split of DNA through the various embryonic stages.

This new evidence that TrxG and PcG proteins but not methylated histones remain associated with DNA through replication could have significant impacts on how scientists study epigenetic marks.

Instead of focusing on numerous types of modified histones, it is probably more practical to assess which non-histone proteins remain stably associated with their sites on DNA following DNA replication, as they may potentially carry essential epigenetic information by restoring the state of histone modifications in the daughter cell, according to Dr. Mazo.

"It is also important to understand whether the way nucleosomes are assembled in mammalian cells is similar to that detected in Drosophila embryos and whether these mechanisms remain unchanged during cell differentiation in development and disease," he added.


Story Source:

The above story is based on materials provided by Thomas Jefferson University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Svetlana Petruk, Yurii Sedkov, DanikaM. Johnston, JacobW. Hodgson, KathrynL. Black, SinaK. Kovermann, Samantha Beck, Eli Canaani, HughW. Brock, Alexander Mazo. TrxG and PcG Proteins but Not Methylated Histones Remain Associated with DNA through Replication. Cell, 2012; DOI: 10.1016/j.cell.2012.06.046

Cite This Page:

Thomas Jefferson University. "Histone-modifying proteins, not histones, remain associated with DNA through replication." ScienceDaily. ScienceDaily, 23 August 2012. <www.sciencedaily.com/releases/2012/08/120823143059.htm>.
Thomas Jefferson University. (2012, August 23). Histone-modifying proteins, not histones, remain associated with DNA through replication. ScienceDaily. Retrieved January 27, 2015 from www.sciencedaily.com/releases/2012/08/120823143059.htm
Thomas Jefferson University. "Histone-modifying proteins, not histones, remain associated with DNA through replication." ScienceDaily. www.sciencedaily.com/releases/2012/08/120823143059.htm (accessed January 27, 2015).

Share This


More From ScienceDaily



More Plants & Animals News

Tuesday, January 27, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

How To: Mixed Green Salad Topped With Camembert Cheese

How To: Mixed Green Salad Topped With Camembert Cheese

Rumble (Jan. 26, 2015) Learn how to make a mixed green salad topped with a pan-seared camembert cheese in only a minute! Music: Courtesy of Audio Network. Video provided by Rumble
Powered by NewsLook.com
Water Fleas Prepare for Space Voyage

Water Fleas Prepare for Space Voyage

Reuters - Innovations Video Online (Jan. 26, 2015) Scientists are preparing a group of water fleas for a unique voyage into space. The aquatic crustaceans, known as Daphnia, can be used as a miniature model for biomedical research, and their reproductive and swimming behaviour will be tested for signs of stress while on board the International Space Station. Jim Drury went to meet the team. Video provided by Reuters
Powered by NewsLook.com
Husky Puppy Plays With Ferret

Husky Puppy Plays With Ferret

Rumble (Jan. 26, 2015) It looks like this 2-month-old Husky puppy and the family ferret are going to be the best of friends. Look at how much fun they&apos;re having together! Credit to &apos;Vira&apos;. Video provided by Rumble
Powered by NewsLook.com
Scientists Model Flying, Walking Drone After Vampire Bats

Scientists Model Flying, Walking Drone After Vampire Bats

Buzz60 (Jan. 26, 2015) Swiss scientists build a new drone that can both fly and walk, modeling it after the movements of common vampire bats. Jen Markham (@jenmarkham) has the story. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins