Difference between Eukaryotic and
In prokaryotes, the promoter consists of two
short sequences at -10 and -35 positions upstream from the
transcription start site.
- The sequence at -10 is called the
Pribnow box, or the -10 element, and usually consists of the
six nucleotides TATAAT. The Pribnow box is
absolutely essential to start transcription in prokaryotes.
- The other sequence at -35 (the -35
element) usually consists of the six nucleotides TTGACA. Its
presence allows a very high transcription rate.
Eukaryotic promoters are extremely diverse
and are difficult to characterize. They typically lie upstream
of the gene and can have regulatory elements several kilobases
away from the transcriptional start site. In eukaryotes, the
transcriptional complex can cause the DNA to bend back on
itself, which allows for placement of regulatory sequences far
from the actual site of transcription. Many eukaryotic
promoters, contain a TATA box (sequence
TATAAA), which in turn binds a TATA binding
protein which assists in the formation of the RNA polymerase
transcriptional complex. The TATA box typically lies very
close to the transcriptional start site (often within 50