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Team makes genome breakthrough

Following the complete sequencing of the human genome there remain layers of unresolved mysteries as to how genetic materials are regulated, but a group of Academia Sinica scientists recently shed some new light as to how certain genetic expressions may be switched on or off.

The team, led by Academia Sinica's Institute of Biological Chemistry director Tsai Ming-Daw (蔡明道) and Juan Li-jung (阮麗蓉), an assistant research fellow at Academia Sinica's genomics research center, is due to publish the results in Nature magazine, an international science weekly.

"In addition to DNA sequences, epigenetic regulation also plays a role in genetic expressions," Juan told the Taipei Times in a telephone interview last night.

Epigenetic regulation refers to the different genetic expressions the same DNA sequence may incur because of a change in the histone proteins, which are wrapped around DNA sequences, Juan said.

For example, normally tumor suppressors in our nuclei are turned on. However, an alteration in the histone protein around the suppressors may cause it to be turned off, causing a cancer to form, she said.

Though the team's research target RBP2 -- an enzyme and a histone modifier -- was discovered years ago, the team is the first to have successfully found the specific DNA sequence that it recognized, she said.

"This is exciting because hundreds of histone modifiers have been identified, but few are known to recognize specific DNA sequences," she said. "It is significant that with random sequencing tools producing thousands of DNA sequences, we proved when associated with CCGCCC, RBP2 acts as a histone demethylase and removes trimethyl groups attached to histones ... confirming that histones with three methyl groups act as optional modifiers of the DNA sequence."

Juan said many cancer patients have abnormally high RBP2 levels in their cells, which is a clue that the enzyme may be the culprit.

However, "it is all speculation until further evidence is found," she said.

The team's next step is to find out exactly which gene RBP2 is associated with, she said.
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