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“So must the Son of Man be lifted up, that whoever believes in Him should not perish but have eternal life”

John 3:15

Nucleus

DNA

Cytoplasm

Messenger RNA

[the ‘photocopy’ of the protein recipe]

Now to

EXIT the

nucleus

Nucleus

There are about 3000 to 4000 nuclear pores on the surface of each nucleus!

Nuclear pore

The word 'PORE' is derived from the Greek 'poros' which means 'passage'

The pore is not just a HOLE in the wall of the nucleus.

‘Nuclear pore complexes control the flow into and out of the nucleus and check the credentials of all large molecules attempting to pass through ... By any standards a nuclear pore is a piece of really smart biological engineering. A nuclear pore is a sophisticated biological entry and exit control system guarding the contents and work of the 'Head Office' of the cell, the nucleus.’

British Society for Cell Biology

Before the Messenger RNA [mRNA] can leave the nucleus it must be tagged with an EXPORT SEQUENCE TAG. This tag gives authorization for the mRNA to leave the cell. The pore will not allow the recipe to leave the nucleus unless the export tag is present.

The tag acts as a chaperone, binding to the mRNA and escorting it through the nuclear pore into the cytoplasm. Once out into the cytoplasm, the exported cargo is released and the chaperone returns back into the nucleus to await fresh transportation duties!

“Nuclear pores ... are built from 30 different proteins” – Science Daily (June 12, 2010)

Schematic Drawing of

a Nuclear Pore

Cytoplasmic filament

Cytoplasmic ring

Nuclear envelope

[wall of the nucleus]

Central pore

Nuclear ring

Nuclear basket

The Nuclear pores, which are made from proteins, will allow the recipe for making a protein (mRNA) out into the cytoplasm. CONUNDRUM - Which came first?