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Title:  "Packaging RNA" Really Delivers
Date:   August 14, 1998




August 14, 1998

For more information on these science news and feature story
tips, please contact the public information officer at the end of
each item at (703) 306-1070.  Editor: Bill Noxon

                 "PACKAGING RNA" REALLY DELIVERS

   Although it doesn't get the same kind of attention as its
relative (DNA), RNA is the real workhorse of the gene world.
Known for its duties as messenger, transcriber, translator and
enzyme, RNA has recently been found performing escort duty to DNA
molecules.
   National Science Foundation (NSF)-funded researcher Peixuan
Guo of Purdue University has observed packaging RNA, or "pRNA,"
in this new role during his study of the virus known as
bacteriophage Phi 29.  The findings are published in a recent
issue of the journal Molecular Cell.
   Bacteriophages are viruses that infect bacteria, and they may
use DNA or RNA as genetic material.  After they enter a bacterial
cell, bacteriophages take over the cell's machinery to make new
copies of their own genetic material and protective protein
shell, or "capsid".  What has puzzled scientists is that
bacteriophages make new capsids first, then somehow insert the
replicated copies of their genes into the capsid.
   Guo found that, in the case of Phi 29 (a DNA virus), six pRNA
molecules could form hexagon shaped rings that drive viral DNA
into the capsid.  The RNA hexagon attaches itself to the viral
capsid and then turns like a wrench on a bolt, which forces the
DNA through the pRNA molecule and into the capsid. Although pRNA
has been found in other kinds of bacteriophages, Guo's study is
the first to show pRNA performing this particular feat.
[Greg Lester]

         NSF PROGRAM RECEIVES TECHNOLOGY TRANSFER AWARD

   NSF's Industry/University Cooperative Research Centers (IUCRC)
received an award from the Technology Transfer Society at its
annual conference July 28 in Chicago.
   The Justin Morrill Award is given to organizations that
establish high standards for technology transfer activities, make
significant contributions to society and promote positive
practices that influence public policy.
   NSF's $4-million annual IUCRC program in the Directorate of
Engineering has resulted in a return of $75 million in research
investments by member firms and other sponsors, according to one
of the Morrill Award nomination summaries.
   More than 75 percent of industry's support to university R&D
comes through industry-university centers, such as IUCRCs.  The
IUCRC program was developed in the early 1970s.  [Bill Noxon]

                COMPUTER SIMULATION DEMONSTRATES
                    "BREATHING" ENZYME ACTION

   Using powerful supercomputers, NSF-supported researchers have
unlocked the mystery surrounding one of the fastest, most
efficient enzymes in the human body.  Acetylcholinesterase (AChE)
works to instantly stop transmissions from one nerve cell to the
next nerve or muscle cell.
   AChE catalyzes the chemical reaction that breaks up
acetylcholine (ACh), a neurotransmitter, thereby serving as the
off-switch for the transmission.  The speed of this process has
puzzled researchers since the structure of AChE was first modeled
in 1991.  The active site, where the reaction takes place, was
found deep inside a groove on AChE -- a groove too narrow to
admit ACh quickly.
   Using large-scale computer simulations run at the San Diego
Supercomputer Center, Andrew McCammon of the University of
California, San Diego has shown how AChE does its job: by
"breathing".  The simulations show that this flexing motion
causes AChE to inhale and exhale ACh molecules almost as fast as
if the groove was always open.  Why, then, is the channel blocked
at all?
   McCammon's research has demonstrated that this motion keeps
larger molecules out of the space intended for ACh.  This finding
shows that enzymes can use movements to select particular
substrates in crowded environments like the inside of a living
organism.  This work, first published in the August 4 issue of
the Proceedings of the National Academy of Sciences, also
demonstrates the power of using computer simulations to gain
insight on major biological problems.  [Greg Lester]
   For more information on AChE, see:
http://chemcca10.ucsd.edu/ache_animated.html

                              -NSF-