Invention allows for precise gene control

DNA helices

Credit: NIGMS

A new way to control genes may provide a better understanding of cancers and aid the development of new therapies.

The key to the method is an invention called SunTag, a series of molecular hooks for hanging multiple copies of biologically active molecules onto a single protein scaffold used to target genes or other molecules.

Compared to molecules assembled without these hooks, those incorporating SunTag can greatly amplify biological activity.

SunTag was developed by researchers in the lab of Ron Vale, PhD, of the University of California, San Francisco (UCSF), and described in two papers published in Cell.

In one paper, the authors recount how they used SunTag to greatly amplify the light-emitting signal from the green fluorescent protein commonly used to label molecules within cells.

In another paper, the researchers explain how they used SunTag to supercharge a variation of a biochemical approach known as CRISPR.

CRISPR is a technique that emerged a few years ago as a way to edit DNA anywhere within the genome.

The UCSF researchers adapted CRISPR to activate genes or interfere with their activity in a reversible way without altering DNA. The team believes this capability might make previous methods for probing poorly understood cellular functions obsolete.

“With these techniques, we can fine-tune the activity of genes within cells, and this has broad implications for the reprogramming of cells,” said Jonathan Weissman, PhD, also of UCSF.

Scientists previously reported ways to activate or interfere with genes using CRISPR, but Dr Vale said these methods were inefficient, especially for activating genes.

“It depends on the gene, but this new approach appears to amplify gene-switching by as much as 50-fold,” he said. “It’s a much more robust way of activating genes.”

CRISPR with SunTag sheds light on cancers

CRISPR is a natural system that bacteria use to defend themselves against viruses. The basis for CRISPR applications in the lab is a protein called Cas9, a chassis into which scientists can insert any specific RNA partner molecule.

The selected RNA serves as an adaptor that determines the target anywhere within the genome. The researchers attached SunTag to this chassis, enabling one Cas9 to recruit many copies of a protein to a specific DNA sequence.

The adaptation of SunTag for CRISPR activation makes it possible to systematically probe the biological roles of all genes within the genome in a single experiment, the team said.

They used CRISPR activation to identify a number of tumor suppressor genes that inhibit the growth of cancer cells. In future studies, they plan to use CRISPR activation to reveal mechanisms by which cancer cells develop resistance to anticancer drugs, a process that typically involves gene activation.

Will RNA interference become obsolete?

CRISPR interference has the potential to render RNA interference obsolete, according to Dr Weissman.

Unlike conventional RNA interference techniques, CRISPR interference allows any number of individual genes to be silenced at the same time. In addition, there is little risk of turning off untargeted genes the way RNA interference techniques do.

RNA interference blocks the messenger RNA that drives protein protection based on the blueprint contained within a gene’s DNA sequence. By preventing protein production, RNA interference may be used to get around the problem of difficult-to-target proteins, a frequent challenge in drug development.

But CRISPR interference acts one step earlier in the cell’s protein-manufacturing process.

“The horse has already left the barn with RNA interference, in the sense that the RNA message already has been transcribed from DNA,” Dr Weissman said. “With CRISPR interference, we can prevent the message from being written.”

DNA helices

Credit: NIGMS

A new way to control genes may provide a better understanding of cancers and aid the development of new therapies.

The key to the method is an invention called SunTag, a series of molecular hooks for hanging multiple copies of biologically active molecules onto a single protein scaffold used to target genes or other molecules.

Compared to molecules assembled without these hooks, those incorporating SunTag can greatly amplify biological activity.

SunTag was developed by researchers in the lab of Ron Vale, PhD, of the University of California, San Francisco (UCSF), and described in two papers published in Cell.

In one paper, the authors recount how they used SunTag to greatly amplify the light-emitting signal from the green fluorescent protein commonly used to label molecules within cells.

In another paper, the researchers explain how they used SunTag to supercharge a variation of a biochemical approach known as CRISPR.

CRISPR is a technique that emerged a few years ago as a way to edit DNA anywhere within the genome.

The UCSF researchers adapted CRISPR to activate genes or interfere with their activity in a reversible way without altering DNA. The team believes this capability might make previous methods for probing poorly understood cellular functions obsolete.

“With these techniques, we can fine-tune the activity of genes within cells, and this has broad implications for the reprogramming of cells,” said Jonathan Weissman, PhD, also of UCSF.

Scientists previously reported ways to activate or interfere with genes using CRISPR, but Dr Vale said these methods were inefficient, especially for activating genes.

“It depends on the gene, but this new approach appears to amplify gene-switching by as much as 50-fold,” he said. “It’s a much more robust way of activating genes.”

CRISPR with SunTag sheds light on cancers

CRISPR is a natural system that bacteria use to defend themselves against viruses. The basis for CRISPR applications in the lab is a protein called Cas9, a chassis into which scientists can insert any specific RNA partner molecule.

The selected RNA serves as an adaptor that determines the target anywhere within the genome. The researchers attached SunTag to this chassis, enabling one Cas9 to recruit many copies of a protein to a specific DNA sequence.

The adaptation of SunTag for CRISPR activation makes it possible to systematically probe the biological roles of all genes within the genome in a single experiment, the team said.

They used CRISPR activation to identify a number of tumor suppressor genes that inhibit the growth of cancer cells. In future studies, they plan to use CRISPR activation to reveal mechanisms by which cancer cells develop resistance to anticancer drugs, a process that typically involves gene activation.

Will RNA interference become obsolete?

CRISPR interference has the potential to render RNA interference obsolete, according to Dr Weissman.

Unlike conventional RNA interference techniques, CRISPR interference allows any number of individual genes to be silenced at the same time. In addition, there is little risk of turning off untargeted genes the way RNA interference techniques do.

RNA interference blocks the messenger RNA that drives protein protection based on the blueprint contained within a gene’s DNA sequence. By preventing protein production, RNA interference may be used to get around the problem of difficult-to-target proteins, a frequent challenge in drug development.

But CRISPR interference acts one step earlier in the cell’s protein-manufacturing process.

“The horse has already left the barn with RNA interference, in the sense that the RNA message already has been transcribed from DNA,” Dr Weissman said. “With CRISPR interference, we can prevent the message from being written.”

DNA helices

Credit: NIGMS

A new way to control genes may provide a better understanding of cancers and aid the development of new therapies.

The key to the method is an invention called SunTag, a series of molecular hooks for hanging multiple copies of biologically active molecules onto a single protein scaffold used to target genes or other molecules.

Compared to molecules assembled without these hooks, those incorporating SunTag can greatly amplify biological activity.

SunTag was developed by researchers in the lab of Ron Vale, PhD, of the University of California, San Francisco (UCSF), and described in two papers published in Cell.

In one paper, the authors recount how they used SunTag to greatly amplify the light-emitting signal from the green fluorescent protein commonly used to label molecules within cells.

In another paper, the researchers explain how they used SunTag to supercharge a variation of a biochemical approach known as CRISPR.

CRISPR is a technique that emerged a few years ago as a way to edit DNA anywhere within the genome.

The UCSF researchers adapted CRISPR to activate genes or interfere with their activity in a reversible way without altering DNA. The team believes this capability might make previous methods for probing poorly understood cellular functions obsolete.

“With these techniques, we can fine-tune the activity of genes within cells, and this has broad implications for the reprogramming of cells,” said Jonathan Weissman, PhD, also of UCSF.

Scientists previously reported ways to activate or interfere with genes using CRISPR, but Dr Vale said these methods were inefficient, especially for activating genes.

“It depends on the gene, but this new approach appears to amplify gene-switching by as much as 50-fold,” he said. “It’s a much more robust way of activating genes.”

CRISPR with SunTag sheds light on cancers

CRISPR is a natural system that bacteria use to defend themselves against viruses. The basis for CRISPR applications in the lab is a protein called Cas9, a chassis into which scientists can insert any specific RNA partner molecule.

The selected RNA serves as an adaptor that determines the target anywhere within the genome. The researchers attached SunTag to this chassis, enabling one Cas9 to recruit many copies of a protein to a specific DNA sequence.

The adaptation of SunTag for CRISPR activation makes it possible to systematically probe the biological roles of all genes within the genome in a single experiment, the team said.

They used CRISPR activation to identify a number of tumor suppressor genes that inhibit the growth of cancer cells. In future studies, they plan to use CRISPR activation to reveal mechanisms by which cancer cells develop resistance to anticancer drugs, a process that typically involves gene activation.

Will RNA interference become obsolete?

CRISPR interference has the potential to render RNA interference obsolete, according to Dr Weissman.

Unlike conventional RNA interference techniques, CRISPR interference allows any number of individual genes to be silenced at the same time. In addition, there is little risk of turning off untargeted genes the way RNA interference techniques do.

RNA interference blocks the messenger RNA that drives protein protection based on the blueprint contained within a gene’s DNA sequence. By preventing protein production, RNA interference may be used to get around the problem of difficult-to-target proteins, a frequent challenge in drug development.

But CRISPR interference acts one step earlier in the cell’s protein-manufacturing process.

“The horse has already left the barn with RNA interference, in the sense that the RNA message already has been transcribed from DNA,” Dr Weissman said. “With CRISPR interference, we can prevent the message from being written.”