Featured Research

from universities, journals, and other organizations

New Technology Makes It Possible To See Ubiquitin-modified Proteins Inside Living Cells

Date:
October 12, 2004
Source:
University Of Michigan Medical School
Summary:
Researchers at the University of Michigan Medical School and Howard Hughes Medical Institute have found a way to see proteins in cells that have been tagged by a molecular “sticky note” called ubiquitin.

In this image of cells from the U-M study, the green color shows the location of unmodified Jun in the nucleus, while the red color shows ubiquitin-modified Jun located in lysosomes in the cytoplasm.
Credit: Photo Tom Kerppola, Ph.D., University of Michigan

Researchers at the University of Michigan Medical School and Howard Hughes Medical Institute have found a way to see proteins in cells that have been tagged by a molecular “sticky note” called ubiquitin.

“This technology allows us to see, under a microscope, proteins modified by ubiquitin inside the cell,” says Tom K. Kerppola, Ph.D., an associate professor of biological chemistry in the Medical School and an HHMI associate investigator. “Visualization gives us a direct connection to cellular processes that we could only study in test tubes or indirectly before.”

In a paper published online this week in the early edition of the Proceedings of the National Academy of Sciences, Kerppola and Deyu Fang, M.D., Ph.D., a U-M research investigator, describe the first use of a technology called ubiquitin-mediated fluorescence complementation to study a cell-signaling mechanism called ubiquitination.

In this process, a small peptide called ubiquitin is linked to a protein in ways that can change the protein's function and location within the cell. Originally, scientists thought ubiquitin was simply a universal “destroy me” signal for unneeded or harmful proteins, but it has recently been found to be associated with many other cellular functions.

“The same ubiquitin signal can cause one protein to be degraded, but another protein to be moved to a new location,” Kerppola says. “We're interested in learning how this works.”

In their PNAS paper, Kerppola and Fang describe how ubiquitin latched onto Jun - a protein involved in cell growth and gene transcription – and moved Jun from its usual location in the cell's nucleus into hollow spheres called lysosomes in the cytoplasm outside the nucleus. Filled with digestive enzymes, lysosomes break down unwanted proteins into amino acids the cell recycles to make new proteins.

“Jun's function in the nucleus is transient and time-dependent,” Kerppola says. “If it's turned on and doesn't get turned off, that's not normal. Prolonged signaling causes aberrant growth and other problems for the cell.”

“When ubiquitin is attached to Jun, the complex is transported to the lysosome getting it away from DNA in the nucleus and preventing Jun from continuing its normal gene

transcription function,” he adds. “This is a new way for the cell to eliminate the function of a transcription factor.”

U-M scientists also discovered that an E3 ligase binding enzyme called Itch was a key player in the process. “Itch is the adapter,” Kerppola says. “It tags Jun with ubiquitin, and is necessary for the protein to be targeted to the lysosome.”

If Itch doesn't recognize Jun, Kerppola explains, the level of Jun builds up in the cell, which can alter the regulation of gene transcription and cell growth.

“Applying ubiquitin-mediated fluorescence technology to Jun made it possible to discover new information on how Jun turnover is controlled in cells,” Kerppola says.

The technology uses complementary fragments of a fluorescent protein, which are fused to ubiquitin and to the target protein being studied. When ubiquitin is linked to the target protein, the fragments of the fluorescent protein come together and produce a bright spot of glowing color, which can be seen with a fluorescence microscope. This allows scientists to determine the location of the ubiquitinated protein in the cell.

“Location is important,” Kerppola adds, “because proteins must get to their sites of action in order to do their jobs. Each protein must fulfill many different functions in different cells and in response to different stimuli. It is the variety of modifications and interactions with partners that enable the same protein to accomplish different tasks. With this technology, we are able to see the subpopulation of a protein that is modified by ubiquitin or interacts with a particular partner.”

Scientists in Kerppola's laboratory have used bimolecular fluorescence complementation methods to study protein interactions and signaling pathways, in addition to ubiquitination. While the technology should be generally applicable to most interactions, it does have some limitations.

“The assay requires the two fragments of the fluorescent protein to come together,” Kerppola says. “If they can't get together, the assay doesn't work. It's quite good at identifying the location where something happens in the cell, but the timing of the interaction is more difficult to study, since it takes about an hour for the fluorescent proteins to become visible.”

Kerppola and Fang's research is funded by the Howard Hughes Medical Institute, the Human Frontiers Science Program, and a grant from the National Cancer Institute to the U-M's Cancer Biology Training Program.

Citation : PNAS published October 5, 2004 , 10.1073/pnas.0404445101

For more information on related research:http://sitemaker.umich.edu/kerppola


Story Source:

The above story is based on materials provided by University Of Michigan Medical School. Note: Materials may be edited for content and length.


Cite This Page:

University Of Michigan Medical School. "New Technology Makes It Possible To See Ubiquitin-modified Proteins Inside Living Cells." ScienceDaily. ScienceDaily, 12 October 2004. <www.sciencedaily.com/releases/2004/10/041012094822.htm>.
University Of Michigan Medical School. (2004, October 12). New Technology Makes It Possible To See Ubiquitin-modified Proteins Inside Living Cells. ScienceDaily. Retrieved October 1, 2014 from www.sciencedaily.com/releases/2004/10/041012094822.htm
University Of Michigan Medical School. "New Technology Makes It Possible To See Ubiquitin-modified Proteins Inside Living Cells." ScienceDaily. www.sciencedaily.com/releases/2004/10/041012094822.htm (accessed October 1, 2014).

Share This



More Matter & Energy News

Wednesday, October 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

US Police Put Body Cameras to the Test

US Police Put Body Cameras to the Test

AFP (Oct. 1, 2014) Police body cameras are gradually being rolled out across the US, with interest surging after the fatal police shooting in August of an unarmed black teenager. Duration: 02:18 Video provided by AFP
Powered by NewsLook.com
Raw: Japan Celebrates 'bullet Train' Anniversary

Raw: Japan Celebrates 'bullet Train' Anniversary

AP (Oct. 1, 2014) A ceremony marking 50 years since Japan launched its Shinkansen bullet train was held on Wednesday in Tokyo. The latest model can travel from Tokyo to Osaka, a distance of 319 miles, in two hours and 25 minutes. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Robotic Hair Restoration

Robotic Hair Restoration

Ivanhoe (Oct. 1, 2014) A new robotic procedure is changing the way we transplant hair. The ARTAS robot leaves no linear scarring and provides more natural results. Video provided by Ivanhoe
Powered by NewsLook.com
Argentina's Tax Evaders Detected, Hunted Down by Drones

Argentina's Tax Evaders Detected, Hunted Down by Drones

AFP (Sep. 30, 2014) Argentina doesn't only have Lionel Messi the footballer, it has now also acquired "Mesi" the drone system which monitors undeclared mansions, swimming pools and soy fields to curb tax evasion in the country. Duration: 01:18 Video provided by AFP
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


Space & Time

Matter & Energy

Computers & Math

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