Skip to main content

Researchers find a completely new DNA binding protein


The basic premises underlying gene expression—when and where genes are turned on and off—were worked out in bacteria by François Jacob and Jacques Monod in the middle of the twentieth century. The expression of a gene typically relies on one or more proteins binding to a specific DNA sequence near the gene of interest. These proteins are called transcription factors since they regulate the transcription of genes into RNA, the first step in turning them into proteins.At this point, many different families of related transcription factors have been defined. And, as more and more genomes have been sequenced, it was easy
to get the impression that we had a complete catalog. But now, researchers at UCSF have discovered a new type of never-seen-before DNA binding protein in an organism called Candida albicans.
C. albicans is a fungus. It is a strain of yeast that resides in our guts, usually on very peaceable terms with the bacteria that make up our microbiome. Occasionally, it oversteps its bounds to cause thrush, an infection of the mouth. It can also infect other dark, moist, bodily orifices. (Especially if you spend all summer in a wet bathing suit.)
These yeast can be “white” or “opaque." These two states have the same genomes, but they look different because they express a different set of genes—much like differences between human skin cells and human muscle cells. White cells beget white cells, opaque cells beget opaque cells, and random switching between the two types happens only once in 10,000 generations.
There are five transcriptional factors known to regulate white-opaque switching. But this group at UCSF thought that might not be all. So they looked for genes that (a) were expressed only in opaque cells that (b) contained a DNA sequence that one of these five known factors could stick to.
They found only one gene that fit both criteria; they named it WOR3 (white-opaque regulator-3). When they put WOR3 into white cells, it made them turn opaque. When they deleted it, opaque cells stayed opaque at temperatures that generally get them to turn white. So this gene promotes opacity, which none of the other five regulators do.
And, like the other five regulators, the WOR3 protein binds to specific DNA sequences. This was a bit of a surprise, since it does not resemble any other DNA or RNA binding proteins. Proteins similar to WOR3 were found only in closely related fungi, so it probably arose fairly recently in evolutionary terms—about 300 million years ago. (Yes, from an evolutionary perspective, that's relatively recent.)
As the authors themselves admit, without a three dimensional structure of the protein, it is difficult to know if it really binds DNA in a unique way. It may be that the order of the amino acids that make up the protein is different from anything we know of, but it can still fold up into something that looks familiar.
They note that, besides the obvious part about a brand new DNA binding protein, their most important insight is that there are still new things out there to be discovered. Just because we know about a lot of proteins, DNA sequences, and mechanisms of transcriptional regulation, we shouldn’t get complacent and think that we know them all.

Enhanced by Zemanta

Comments

Popular posts from this blog

LG’s first flexible OLED phone due before the year is out

LG plans to launch a flexible OLED smartphone before the end of the year, the company’s VP of mobile has confirmed, though it’s unclear to what extent the work-in-progress handset will actually flex. The OLED panel in question is the handiwork of LG Display according to VP of LG mobile Yoon Bu-hyun, the WSJ  reports, with the proposed device set to launch sometime in Q4. LG Display’s work on flexible OLEDs has been underway for some time, though the company’s efforts have perhaps been overshadowed somewhat by rival Samsung’s YOUM development. Last year, according to a Korea Times report, LG Display was preparing for

Syrian Electronic Army claims credit for CBS Twitter accounts hack

Yesterday, several of CBS ’s Twitter accounts were hacked, including its main account, and its accounts for 60 Minutes, 48 Hours, and CBS Denver. The hackers got into the account and tweeted a series of things relating to President Obama and the United States being in cahoots with Al-Qaeda . The tweets also had links that led users to malware-infested sites. While CBS was able to regain access to its accounts, it was unable to figure out who was behind the attacks, until now. The Syrian Electronic Army , the same group that hacked 3 of the BBC’s Twitter accounts, claimed

Can Technology Do a Better Job of Finding Bombs?

 With the horrifying images of the Boston Marathon bombing still much too fresh in our minds, and with citywide marathons coming up this weekend in London, Hamburg, and Salt Lake City , law enforcement officers and citizens everywhere are asking how to prevent the tragedy from being repeated. As Columbia University School of International and Public Affairs adjunct professor Abraham Wagner observed last year, on the 11th anniversary of 9/11, there’s “no magic bullet o