Navigation Links
Scientists discover a mechanism that can send cells on the road to cancer
Date:4/22/2008

Using a common virus as a tool for investigating abnormal cell proliferation, a team led by scientists at Cold Spring Harbor Laboratory (CSHL) has succeeded in clarifying an intricate series of biochemical steps that shed light on a way that cancer can begin.

The teams findings are the latest in a long and distinguished line of research at CSHL involving adenovirus, a type of virus that causes the common cold in people, but whose genome contains known oncogenes -- genes whose expression can promote cancer under certain conditions.

Adenovirus carries a number of cooperating genes that modulate cell growth in ways were interested in, said William Tansey, Ph.D., who, along with CSHL professors Scott Lowe, Ph.D., and Gregory Hannon, Ph.D., is one of the teams co-leaders and corresponding author of a paper to be published April 22 in Proceedings of the National Academy of Sciences. Other team members include molecular biologists from Stony Brook University in New York.

Using a Tumor Virus to Illuminate Function

The team focused on an adenoviral oncogene called E1A, and a protein that it codes for with the same name. Both have received a great deal of attention over the years, said Dr. Tansey, and to understand why, it helps to understand why viruses -- in this case, adenovirus, a DNA tumor virus -- is useful to us. We use them as you would use a flashlight, to illuminate important processes inside the cell that help us understand what goes awry in oncogenesis.

Viruses cant reproduce on their own. A DNA virus like adenovirus is little more than a tiny, double-stranded segment of DNA enclosed within a protein shell. It must find a way to enter the nucleus of a living cell and hijack the cells reproductive machinery in order to reproduce itself. Its not adenovirus itself, but the things it does when it enters a cell, that really interest us, Dr. Tansey explained. By looking, in particular, at the activity of the proteins adenovirus codes for -- proteins like E1A -- we are tapping into a kind of natural growth-control mechanism.

The utility of DNA tumor viruses for cancer research is based on the premise that theyve evolved to target the minimum number of cellular pathways necessary for virus propagation, said Dr. Lowe. When things go awry, understanding how a tumor virus like adenovirus promotes cancer can reveal, in turn, the most vulnerable pathways and nodes that are linked to tumorigenesis, Dr. Hannon added.

Commandeering the Cell Cycle

Because a tumor virus needs to commandeer the reproductive machinery of a living cell to survive, it must force the host cell to enter the reproductive, or S-phase, of its cycle. Past research has demonstrated that a protein called E2F is central in the process by which S-phase is activated. When the cell is not reproducing, E2F is known to be inhibited by its binding to another protein, called Rb, or retinoblastoma protein.

Its this regulated association of E2F and Rb that is one of the primary mechanisms through which cells normally progress into S-phase, Dr. Tansey said. The E1A protein, after binding Rb, is capable of physically pulling it off the E2F molecule. This unleashes the cell to replicate its DNA. And this, in turn, can promote transformations associated with cancer.

Recently, its been shown that E1As cancer-promoting activity is more extensive, also involving a gene-regulating protein called p400. Until the CSHL/Stony Brook team published its current paper, no one knew how E1As binding with p400 affected the process.

E1As Role in Another Oncogenic Pathway

The team knew from prior studies that when the E1A and p400 proteins were bound to one another, cellular growth control was disrupted. The question was why this potentially oncogenic effect occurred. What mechanisms were set in motion by the binding of these two proteins?

They hypothesized that the answer could be found in the activity of yet another protein, called Myc, which Dr. Tansey has spent much of his career studying. Myc is an oncoprotein: one that is important in a great many regulatory processes in the cell, and which, when overexpressed, can cause dysregulation that leads to cancer.

Prior work had shown that when E1A was present in a cell, the potentially dangerous Myc protein was stable -- it did not degrade naturally. In new experiments, Tansey and colleagues found that E1As stabilization of the Myc protein was accomplished not, as was suspected by some, by directly inhibiting its degradation in a cellular component called the proteosome, which destroys proteins. Rather, E1A stabilized Myc by promoting its binding with p400.

To recap the complex sequence of events: E1A, when present in a cell, binds to p400. That protein, in turn, forms a complex with Myc which accounts for Mycs stability in cells in which E1A is present. Close study showed that the piece of the E1A protein that was important for stabilizing Myc was the same piece that bound to p400, Dr. Tansey said. And just as E1A can pull the Rb protein away from E2F, initiating a cascade of pathologies potentially leading to oncogenesis, so does the ability of E1A to bind p400 -- and via that connection to engage Myc -- stabilize that oncoprotein and open the door to tumorigenesis.

We know now that the interaction of E1A and p400 is very important in terms of regulating cell growth in normal and cancer cells, Dr. Tansey said. So were taking a cue from the history of work on adenoviruses and were leaving E1A behind to concentrate on Myc and p400. For us, now, the next step is to learn more about the p400-Myc connection.


'/>"/>

Contact: Jim Bono
bono@cshl.edu
516-367-8455
Cold Spring Harbor Laboratory
Source:Eurekalert

Related medicine news :

1. Scientists identify novel way to prevent cardiac fibrosis
2. Scientists Explore Human Gene Pool With Help From Microsoft Research
3. Scientists obtain anticancer medicines from the elecampe, a wild plant growing in the Mediterranean
4. Jefferson scientists discovery may help explain smoking-pancreatic cancer link
5. With annual deaths from malaria on the rise: Scientists ask where is all the money going?
6. Stem cells and cancer: Scientists investigate a fine balancing act
7. Scientists Block Prostate Cancer Cells Spread
8. Scientists solve mystery of polyketide drug formation
9. Scientists Uncover How HIV Hides Inside Cells
10. Scientists: New technique identifies molecular biomarkers for disease
11. Princeton Professor David W. C. MacMillan Lectured WuXi PharmaTech Scientists
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/12/2016)... ... February 12, 2016 , ... Vail knee specialist Robert LaPrade, MD, ... in 2016 . The list consists of physicians establishing, leading and partnering with ambulatory ... , An Ambulatory Surgery Center, also known as an ASC, is a modern ...
(Date:2/12/2016)... ... February 12, 2016 , ... For Coast Dental dentist Everet Lake, DDS, ... dental assistant Terrell Moore shortly before 7 a.m. to volunteer at Friday’s Dentistry from ... their time and skills to help hundreds of uninsured and underinsured people receive much-needed ...
(Date:2/12/2016)... ... 2016 , ... Homeowners now have a next generation tool ... leading brand of building products, has improved upon its industry-best array of home ... of the ColorView® Exterior Style and Color Selector. Created expressly for the iPad®, ...
(Date:2/12/2016)... (PRWEB) , ... February 12, 2016 , ... ... creating explosive growth in the field of long term care. With that, says ... for well-trained healthcare professionals in administrative roles in long term care environments. His ...
(Date:2/12/2016)... ... , ... Dignity Health named Dr. Scott Bingham the Facility Medical Director of ... is licensed under Dignity Health Arizona General Hospital , which opened last year ... ensure our new freestanding emergency room delivers the highest quality care to Mesa and ...
Breaking Medicine News(10 mins):
(Date:2/12/2016)... 2016  Memorial Hermann Health System has teamed up ... to bring a one-of-a-kind experience to pediatric patients at ... such as 360-degree video and Google Cardboard, Howard was ... – giving the patients and their families an unexpected, ... caught on video . Memorial Hermann ...
(Date:2/12/2016)... DIEGO and SEOUL, South ... Silicon Biosys­tems Menarini and Macrogen, Inc. today announced ... assays and innovative procedures for precision medicine in ... combine Silicon Biosystems, DEPArray™ digital-sorting technology with Macrogen,s ... of tests certified under the Clinical Laboratory Improvement ...
(Date:2/12/2016)... -- OMS Supply, a large provider of oral surgery supplies ... recent launching of their new company website. The OMS ... enhance the user experience and enable practitioners to browse ... --> --> Despite the fact that ... in early 2016, they have already made an unprecedented ...
Breaking Medicine Technology: