Piero
Bianco, PhD, is the first person to film a DNA motor protein
“unzipping” a double-strand of bacterial DNA.
Knowing how DNA unwinds, copies and repairs itself—what
starts it, what stops it and why—is vitally important to
recombinant DNA research and could make possible major advancements
in cancer treatment.
DNA motor proteins are natural drug targets because they allow
DNA to copy and repair itself, causing the uncontrolled cell growth
in cancer. Researchers know that many cancer drugs stop cell
growth, but they don’t know precisely how.
Bianco, an associate professor of microbiology and
immunology, is providing important clues.
To make his movies, he uses a technique he developed called
“laser tweezers,” which he combines with fluorescence
microscopy and laminar flow cells to isolate individual molecules
of DNA and observe the action of the repair machinery in real
time.
Bianco developed his system while a postdoctoral fellow at the
University of California at Davis, in collaboration with
researchers from Lawrence Livermore National Laboratory.
The work culminated in a breakthrough film, which Bianco and
colleagues described in the journal Nature (“Processive
translocation and DNA unwinding by individual RecBCD enzyme
molecules”).
The film features a molecule of Escherichia coli helicase,
called RecBCD, which acts by unzipping the DNA molecule from one
end to the other.
Since then, Bianco has made significant improvements to his filming
technique that have resulted in higher-resolution movies.
Bianco also has adapted his system to investigate other, more
complex bacterial helicases, including RuvAB, a motor protein that
drives a critical late step in genetic recombination called branch
migration.
He is making a series of films that depict, for the first time,
how two key proteins work together in humans to drive recombination
and the exchange of genetic information.
The first, Rad54, is a motor protein. The second, Rad51, is a
type of enzyme known as a recombinase, which catalyzes the exchange
of strands of DNA between two DNA molecules, particularly in paired
maternal and paternal chromosomes.
Bianco has shown that when DNA is collapsed around the
recombinase, it makes it exponentially faster for Rad51 to locate
the correct spot on a strand needing repair.
Bianco’s work goes to the heart of one of the biggest
mysteries in recombinant DNA research: What biomechanical processes
are involved in invading a damaged strand of DNA and how to find
the repair target—a question that has enormous implications
for drug development.
He is now working toward his long-term goal: assembling an
entire recombination reaction.
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