Navigation Links
Molecular gate that could keep cancer cells locked up

In a study published today in Genes & Development, Dr Christian Speck from the MRC Clinical Sciences Centre's DNA Replication group, in collaboration with Brookhaven National Laboratory (BNL), New York, reveal the intricate mechanisms involved in the enzyme that governs DNA duplication during cell division. By developing a sophisticated system using synthetic, chemical and structural biology approaches, the study reveals how a key enzyme involved in duplicating genetic information embraces DNA through a gated system, which opens up at precise positions allowing for a highly regulated replication process. This work enhances current understanding of an essential biological process and suggests a route for stopping cell division in disease such as cancer.

When a cell divides, genetic information is duplicated in a process known as DNA replication. For this to occur, a 'replication machine' is assembled on top of the DNA prior to duplication. A protein complex known as ORC that recognises the DNA replication origin initiates the whole process. Next, an enzyme, MCM2-7 helicase, whose role is to unwind and separate the two strands of the DNA helix, is loaded onto the DNA by the machine system ORC. The helicase is a ring shaped enzyme composed of six subunits (hexamer), though how the ring structure opens and encircles the DNA has, until now, remained a mystery.

Initial theories within in field assumed the helicase to exist in an open ring conformation. Speck's team argued that this would undoubtedly lead to poorly regulated DNA replication with no control or specificity. To examine the helicase activity in more detail, Jingchuan Sun at BNL used an electron microscope and revealed, contrary to initial theories, the helicase actually existed as a closed ring conformation.

To pinpoint where within the six subunits, the helicase opens to encompass the DNA, the team generated linkages that blocked ring opening at various positions. They found that if they blocked one specific interface, between MCM2 and MCM5, DNA could not enter. A small molecule called rapamycin brings the linkages together; such a molecular switch can be used to control DNA entry to the MCM ring and subsequent DNA replication. "Both in the context of our in vitro and in vivo experiments, we showed that opening of the MCM2/MCM5 interface is essential for helicase loading onto DNA," explains Christian.

"The field has known for a while that DNA can pass into the MCM2-7 ring, but has never been sure which MCM subunits are used for regulated helicase loading. By designing an elegant experiment, the Speck laboratory has now shown once and for all that the MCM2-5 is the only DNA entry point," says collaborator Huilin Li at BNL.

In eukaryotes, the MCM2-7 helicase forms a double hexamer (with another MCM2-7 unit) when it is loaded onto DNA. In this study, the group also settled the longstanding dispute surrounding whether the helicase is actually loaded as a single hexamer, which then dimerises, or is loaded as a dimer at the offset. They concluded that the helicase is in fact loaded as a single hexamer before forming a double hexamer.

In a successful collaboration that harnesses the electron microscopy expertise at BNL with the chemical biology and genetic expertise at the MRC Clinical Sciences Centre, the study addresses key questions detailing the processes involved in DNA replication. "Our work is aimed at understanding the molecular mechanism of DNA replication at a fundamental level. Yet our findings could also have important implications, possibly pointing to new ways to fight cancer, because DNA duplication is a prime target to inhibit cancer cell growth," says Christian.


Contact: Christian Speck
MRC Clinical Sciences Centre

Related medicine news :

1. China Diagnostic Reagent Industry (biochemical, molecular & immunodiagnostic) 2016 Forecasts in New Research Report at
2. Immunotherapy, Targeted Molecular Therapies Among Promising New Treatments for Brain Tumors
3. Increasing Molecular Level Understanding of Disease State & Metabolism Drives the Molecular Diagnostics Market, According to New Report by Global Industry Analysts, Inc.
4. Global Molecular Diagnostics Market Report 2014 Edition Now Available at
5. VCU receives grant to study molecular marks left by childhood adverse experiences
6. Rigid connections: Molecular basis of age-related memory loss explained
7. Global Molecular Diagnostics Market Expected to Reach USD 8.7 Billion through 2019: Transparency Market Research
8. Enzyme-inhibition could revolutionize molecular imaging
9. Molecular imaging finds novel way to knock down breast cancer
10. Molecular breast imaging protocol unmasks more cancer
11. Scientists generate long-sought molecular map of critical genetic machinery
Post Your Comments:
Related Image:
Molecular gate that could keep cancer cells locked up
(Date:10/13/2017)... ... October 13, 2017 , ... Lori R. Somekh, founder of ... ElderCounsel, a national organization of elder law and special needs planning attorneys. “Membership in ... It also provides a forum to network with elder law attorneys nationwide,” said Somekh. ...
(Date:10/13/2017)... ... , ... Global Healthcare Management’s 4th Annual Kids Fun Run brought out many ... event, sponsored by Global Healthcare Management’s CEO, Jon Letko, is aimed at getting kids ... of all ages; it is a non-competitive, non-timed event, which is all about having ...
(Date:10/13/2017)... ... 13, 2017 , ... “America On The Brink”: the Christian history of the ... is the creation of published author, William Nowers. Captain Nowers and his wife, ... he spent thirty years in the Navy. Following his career as a naval ...
(Date:10/12/2017)... CITY, Fla. (PRWEB) , ... October 12, 2017 , ... ... cold therapy products, announced today the introduction of an innovative new design of the ... multipurpose pad so you get maximum comfort while controlling your pain while using cold ...
(Date:10/12/2017)... ... October 12, 2017 , ... HMP , a ... of a 2017 Folio Magazine Eddie Digital Award for ‘Best B-to-B Healthcare Website.’ Winners ... October 11, 2017. , The annual award competition recognizes editorial and design excellence across ...
Breaking Medicine News(10 mins):
(Date:10/5/2017)... , Oct. 5, 2017  In response to ... Oral and Maxillofacial Surgeons (AAOMS) released prescribing recommendations ... to be used as a first-line therapy to ... Recognizing the value ... White Paper "Opioid Prescribing: Acute and Postoperative Pain ...
(Date:10/4/2017)... , Oct. 4, 2017  According to the Centers for Disease Control ... of October . PhysicianOne Urgent Care is helping communities across ... NY , by offering no-cost* flu shots through the end of ... by certain health insurance regulations. ... best time to get a flu shot is by the end of ...
(Date:10/2/2017)... Oct. 2, 2017 Diplomat Pharmacy, Inc. (NYSE: ... Software and Consulting, LLC , and named its founder ... based in Tennessee , will operate ... expands EnvoyHealth,s service offerings for health care partners to ... "In an interoperable world, technology ...
Breaking Medicine Technology: