What are the differences between initiation of transcription in prokaryotes and eukaryotes?

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There are significant differences in the process of transcription in prokaryotes versus eukaryotes.

In prokaryotes, transcription occurs in the cytoplasm. Translation of the mRNA into proteins also occurs in the cytoplasm. In eukaryotes, transcription occurs in the cell's nucleus. mRNA then moves to the cytoplasm for translation.

DNA in prokaryotes is much more accessible to RNA polymerase than DNA in eukaryotes. Eukaryotic DNA is wrapped around proteins called histones to form structures called nucleosomes. Eukaryotic DNA is packed to form chromatin. While RNA polymerase interacts directly with prokaryotic DNA, other proteins mediate the interation between RNA polymerase and DNA in eukaryotes.

mRNA produced as a result of transcription is not modified in prokaryotic cells. Eukaryotic cells modify mRNA by RNA splicing, 5' end capping, and addition of a polyA tail.



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Prokaryotes only contain three different promoter elements: -10, -35 promoters, and upstream elements.  Eukaryotes contain many different promoter elements: TATA box, initiator elements, downstream core promoter element, CAAT box, and the GC box to name a few.  Eukaryotes have three types of RNA polymerases, I, II, and III, and prokaryotes only have one type.  Eukaryotes form and initiation complex with the various transcription factors that dissociate after initiation is completed.  There is no such structure seen in prokaryotes.  Another main difference between the two is that transcription and translation occurs simultaneously in prokaryotes and in eukaryotes the RNA is first transcribed in the nucleus and then translated in the cytoplasm.  RNAs from eukaryotes undergo post-transcriptional modifications including: capping, polyadenylation, and splicing.  These events do not occur in prokaryotes.  mRNAs in prokaryotes tend to contain many different genes on a single mRNA meaning they are polycystronic.  Eukaryotes contain mRNAs that are monocystronic.  Termination in prokaryotes is done by either rho-dependent or rho-independent mechanisms.  In eukaryotes transcription is terminated by two elements: a poly(A) signal and a downstream terminator sequence.