Pore part 2:  This is an image of a
cross section through a PORE
COMPLEX.  The complex is formed
from a ring of proteins called the
ANNULAR RING that surrounds each
pore.  Eight of these proteins form
the pore complex.  The center of
each pore is an opening of about
9nm.  The pores are large enough so
that ribonuclear proteins like
those destined to become ribosomal
subunits and mRNA can pass through.
Any time you look at a pore you
usually see some RNP passing
through.  In this image you can
also see the chromosomes attached
to the inner membrane ( dark
patches ) and if you look closely
the nuclear lamina ( enclosed in a
box ) can be located. The lamina is
a network of fibers that lies just
under the inner membrane.  It holds
the nucleus together. During
prophase of mitosis an enzyme
called a protein kinase
phosphorylates the lamina protein
and causes it to fall apart.  This
causes the nucleus to fall apart.
Later during telophase the
phosphate is cleaved off and the
nucleus reassembles without the
need for protein synthesis. (SEE
CELL CYCLE).