Featured Research

from universities, journals, and other organizations

Circadian Rhythm: How Cells Tell Time

Date:
June 10, 2009
Source:
UT Southwestern Medical Center
Summary:
The fuzzy pale mold that lines the glass tubes in one researcher's lab doesn't look much like a clock. But this fungus has an internal, cell-based timekeeper nearly as sophisticated as a human's, allowing physiologists to study easily the biochemistry and genetics of body clocks, or circadian rhythms.

Dr. Yi Liu is studying mold that uses a protein called FRQ as the main gear of its biological clock. His research team had found that a sequence of changes in the protein’s chemical structure is used to mark time, a finding that might someday help develop treatments for human sleep disorders.
Credit: Image courtesy of UT Southwestern Medical Center

The fuzzy pale mold that lines the glass tubes in Dr. Yi Liu’s lab doesn’t look much like a clock.

But this fungus has an internal, cell-based timekeeper nearly as sophisticated as a human’s, allowing UT Southwestern Medical Center physiologists to study easily the biochemistry and genetics of body clocks, or circadian rhythms.

In a new study appearing online this week in the Proceedings of the National Academy of Sciences, Dr. Liu and his co-workers have found that this mold, which uses a protein called FRQ as the main gear of its clock, marks time by a sequence of changes in the protein’s chemical structure.

Dr. Liu said the new finding might someday help researchers develop treatments for human sleep disorders and other problems associated with a faulty biological clock.

“This timekeeping protein is really the core component of the circadian clock,” said Dr. Liu, professor of physiology at UT Southwestern and senior author of the study.

Despite the evolutionary distance from mold to man, mechanisms controlling their circadian clocks are very similar. In both, circadian rhythms control many biological processes, including cell division, hormonal release, sleep/wake cycles, body temperature and brain activity.

The researchers employed a fungus called Neurospora, an organism frequently used in studies on genetics and cell processes, especially circadian rhythms. It reproduces in the dark and rests in the light.

A decade ago, Dr. Liu discovered that FRQ controlled the cellular clock in Neurospora by chemical changes of its protein structure. As the day goes on, the cell adds chemical bits called phosphates to the protein. Each new phosphate acts like a clock’s ticking, letting the cell know that more time has passed.

When the number of phosphates added to FRQ reaches a certain threshold, the cell breaks it down, ready to start the cycle again.

The researchers, however, did not know where the phosphates attached to FRQ, how many got added throughout a day, or how they affected the protein’s ability to “tell” time.

In the current study, the researchers used purified FRQ to analyze the specific sites where phosphate groups attach. In all, the researchers found 76 phosphate docking sites.

“This is an extremely high number,” Dr. Liu said. “Most proteins are controlled by only a handful of phosphate sites.”

They also studied how these phosphates are added to FRQ daily and found that two enzymes are responsible for adding most of the phosphate groups in Neurospora. They also found that the total number of phosphates oscillates robustly day by day.

In addition, the researchers created a series of mutations in many of the phosphate docking sites, creating strains of mold that had abnormally short or long daily clocks.

In upcoming studies, the researchers plan to identify which enzymes add phosphates to specific sites and exactly how changes in a particular site affect a cell’s clock.

Other UT Southwestern physiology researchers contributing to the work were co-lead authors Dr. Chi-Tai Tang, postdoctoral researcher, and Dr. Shaojie Li, former postdoctoral researcher; Dr. Joonseok Cha, postdoctoral fellow; Dr. Guocun Huang, assistant instructor; and Dr. Lily Li, former postdoctoral researcher. Researchers from the National Institute of Biological Sciences in China and the Chinese Academy of Sciences also participated.

The study was supported by the National Institutes of Health and the Welch Foundation.


Story Source:

The above story is based on materials provided by UT Southwestern Medical Center. Note: Materials may be edited for content and length.


Cite This Page:

UT Southwestern Medical Center. "Circadian Rhythm: How Cells Tell Time." ScienceDaily. ScienceDaily, 10 June 2009. <www.sciencedaily.com/releases/2009/06/090608182537.htm>.
UT Southwestern Medical Center. (2009, June 10). Circadian Rhythm: How Cells Tell Time. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2009/06/090608182537.htm
UT Southwestern Medical Center. "Circadian Rhythm: How Cells Tell Time." ScienceDaily. www.sciencedaily.com/releases/2009/06/090608182537.htm (accessed July 30, 2014).

Share This




More Health & Medicine News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Health Insurers' Profits Slide

Health Insurers' Profits Slide

Reuters - Business Video Online (July 30, 2014) Obamacare-related costs were said to be behind the profit plunge at Wellpoint and Humana, but Wellpoint sees the new exchanges boosting its earnings for the full year. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Generics Eat Into Pfizer's Sales

Generics Eat Into Pfizer's Sales

Reuters - Business Video Online (July 29, 2014) Pfizer, the world's largest drug maker, cut full-year revenue forecasts because generics could cut into sales of its anti-arthritis drug, Celebrex. Fred Katayama reports. Video provided by Reuters
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:
from the past week

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