IU scientists explore gene silencing

IU scientists have come one step closer to understanding the roots of genetic mutation.

A group of 12 scientists from IU discovered how acquired traits can be passed down from previous generations, according to Thursday’s IU press release.

The process, called epigenetic inheritance, shows that cells don’t know to silence, or stop the function of, some genes based on

information in their DNA sequences. The cells do recognize genetic chemical marks added to the genes, according to the release.

Craig Pikaard, an IU biologist and biochemist, led the team. He earned his Ph.D. from Purdue University in 1985 and his areas of research include plant molecular biology
and the study of chromosomes and gene integrity.

“Importantly, this work shows that silent locus identity is required for, but separable from, actual gene silencing,” Pikaard said. “We’ve found that epigenetic inheritance is a two-step process, with the heritable specification of silent locus identity occurring before actual silencing of the locus can occur.”

Pikaard is the Carlos O. Miller Professor of Plant Growth and Development in the IU College of Arts and Sciences’ Department of Biology and Department of Molecular and Cellular Biochemistry. In 2011, he received approximately $5 million in grants over a five year period to advance the study of plant biology as a Howard Hughes Medical Institute and Gordon and Betty Moore Foundation Investigator.

According to the release, the chemical marks are used as a form of molecular memory, which allows cells to recognize genes and remember to silence them with each new generation.

This work can potentially help in cancer research, as many forms are increasingly seen to have an epigenetic base, according to the release.

It also helps explain the bases of RNA polymerases Pol IV and Pol V, two plan-specific gene-silencing enzymes, according to the release.

Both enzymes were first identified by Pikaard in 1999.

The research tested and identified the relationship between histone deacetylase 6, an emzyme that removes acetyl groups from histones, and CG DNA sequence maintenance methyltransferase, MET1.

Together, methylation can explain the continuance of epigenetic memory that accounts for inactivity for that specific gene, according to the release.  

The enzyme slices off a part of a specific DNA sequence, silencing it.  

“Collectively, our results show that locus identity is perpetuated from generation to generation through the actions of HDA6 and MET1,” Pikaard said in the release.
“These activities are not sufficient to silence the loci but maintain a chromatin state that is reguired for Pol IV recruitment, siRNA biogenesis and RdDM, which is what ultimately silences the loci.”

The scientists’ work was published Thursday in the scientific magazine Molecular Cell.

Follow reporter Kathrine Schulze on Twitter @KathrineSchulze.