The expression of genes can be analogous to building a house.  The blueprints (DNA) contain all necessary information on what to build.  These blueprints must then be copied into a transportable form (mRNA) so that they can be taken to the site of construction (ribosomes, where proteins are made).  Transcription is analogous to copying the blueprint.  However, instead of using a copier machine to produce these transportable copies, biological organisms use the enzyme RNA polymerase (RNAP).  With the help of additional factors, this enzyme can produce mRNA transcripts vital for cell survival. 

The transcription process occurs in three main steps: initiation, elongation, and termination (2).  Initiation occurs when RNAP binds to the DNA, unwinds the region it must copy, and begins to produce the first few nucleotides of the mRNA transcript.  During elongation, RNAP moves or translocates down the DNA transcribing the regions necessary for protein synthesis.  Finally, termination occurs when the mRNA transcript has been completed.  When a sequence at the end of this transcript is exposed, it causes the transcript to be cut and released from the enzyme.  RNAP also releases the DNA so that the enzyme can repeat the process of transcription of other DNAs.

This review will begin by briefly discussing the differences between prokaryotic and eukaryotic transcription.  The majority of the review will then focus on eukaryotic transcription in detail.  This will include a discussion of the components and structural mechanisms involved in the process.  Next, the structure of RNAP will be used to explain how a-amanitin, a harmful toxin, affects human health.  Finally, Kornberg’s structural determinations of RNAP will be applied to other areas of scientific research.  Such areas include embryonic stem cell differentiation and mRNA self-correction mechanisms that may support theories on the origin of life.