Human
cells are made up of the following: a cell nucleus, which contains the genetic
material in the form of DNA; and the cytoplasm, where proteins are built. In
the cell nucleus, the DNA that contains the blueprint for the organism is
rewritten into another form, messenger RNA, in order to transport the
information so that these instructions can be used for protein production.
Separated from the original transcript, the proteins can then be produced in
the cytoplasm. The separation is important because the messenger RNA is not
immediately usable; rather, a precursor (pre-messenger RNA) has to be produced
that still contains areas that have to be removed before the messenger RNA
reaches the cytoplasm. If these areas are not removed beforehand, then
shortened or dysfunctional proteins are produced, which is dangerous for the
cell.
The molecular
machinery that cuts these areas out of the messenger RNA are the
spliceosomes. They contain proteins and another type of transcripts of the DNA,
the snRNA. The snRNA is not translated into proteins like messenger RNA, but
together with the proteins, forms the molecular machinery: the spliceosome. In
human cells, the snRNA of the spliceosomes also moves into the cytoplasm. In
other organisms, such as baker's yeast, which is often used as a model organism
in research, scientists had thought that the snRNA of the spliceosomes never
left the cell nucleus. The reason for the evolutionary development to export
snRNA before incorporation into the spliceosomes of human cells was also a
mystery.
See:
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology
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