Transcription in eukaryotes is far more complex than in prokaryotes. This is because eukaryotes have to deal with more diverse environmental conditions. Also, multicellular organisms obviously have differences in gene expression to have its cells be of different types.
Similarities between eukaryotic and prokaryotic transcription complexes:
1) RNA polymerase is directed by a factor to the appropriate site. (Sigma factor in prokaryotes direct to TATA box). Instead of a simple sigma factor, eukaryotes use different proteins, or transcription factors.
2) RNA polymerase has to turn from closed to open state in order to transcribe
Differences:
1) Much more complex process in eukaryotes. Many more proteins acting as transcription factors. This is necessary for specificity in expressions.
2) Transcription cannot freely occur because of chromatin structure. Tightly packaged chromatin must be opened up to let transcription.
The diagram attached shows transcription factors. (In this future it will be explained, hopefully.)
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