By the end of the
nineteenth century, biologists understood that the gross anatomy of
an organism directly underpinned its life style. One hundred years later,
we can carry this understanding all the way to the molecular level relating
the geometry of individual biomolecules to the way they carry out their
functions. At an intermediate level, we expect different parts of the
cell to perform different functions. The architecture of the rnitochondrion
is so exquisitely interlinked with energy production, and the cytoskeleton
with cell support and movement, that discussing function without a knowledge
of structure is impossible. We would expect the same to apply to the
nucleus, with clearly defined regions carrying out specific functions;
however, the nuclear interior is generally depicted in our textbooks
as a featureless tangle of chromatin fibers. Of course, it is not like
that, and this book is based on the belief that an understanding of
nuclear function goes hand in hand with an understanding of nuclear
architecture. Most examples are chosen from the animal world, simply
because less is known about plant nuclei.
This book also promotes
the idea that the key players in the nucleus Ð the active polymerases
Ð are attached to discrete structures within nuclei. Polymerases were
initially purified and analyzed using approaches that destroyed those
structures, so traditional models for polymerase action attach little
significance to nuclear architecture. I describe briefly the traditional
models, before discussing variants where architecture plays a crucial
role. This book, then, is addressed to students entering the field,
and to those working in it who wish to put their results in this newer
structural context. I leave it to the reader to decide whether this
alternative view provides a better approximation to the truth than the
traditional one. Although this book is intended to be read on its own,
additional material can be found at:
http://www.wiley.com/cook
These web pages
include (i) the figures in full color, (ii) the references cited plus
additional up-to-date ones (with hyperlinks to abstracts and complete
articles where available), (iii) links to related web sites, and (iv)
some questions for review (with answers) and discussion.
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