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By the end of this section, you will be able to:
  • List the steps in eukaryotic transcription
  • Discuss the role of RNA polymerases in transcription
  • Compare and contrast the three RNA polymerases
  • Explain the significance of transcription factors

Prokaryotes and eukaryotes perform fundamentally the same process of transcription, with a few key differences. The most important difference between prokaryotes and eukaryotes is the latter’s membrane-bound nucleus and organelles. With the genes bound in a nucleus, the eukaryotic cell must be able to transport its mRNA to the cytoplasm and must protect its mRNA from degrading before it is translated. Eukaryotes also employ three different polymerases that each transcribe a different subset of genes. Eukaryotic mRNAs are usually monogenic, meaning that they specify a single protein.

Initiation of transcription in eukaryotes

Unlike the prokaryotic polymerase that can bind to a DNA template on its own, eukaryotes require several other proteins, called transcription factors, to first bind to the promoter region and then help recruit the appropriate polymerase.

The three eukaryotic rna polymerases

The features of eukaryotic mRNA synthesis are markedly more complex those of prokaryotes. Instead of a single polymerase comprising five subunits, the eukaryotes have three polymerases that are each made up of 10 subunits or more. Each eukaryotic polymerase also requires a distinct set of transcription factors to bring it to the DNA template.

RNA polymerase I is located in the nucleolus, a specialized nuclear substructure in which ribosomal RNA (rRNA) is transcribed, processed, and assembled into ribosomes ( [link] ). The rRNA molecules are considered structural RNAs because they have a cellular role but are not translated into protein. The rRNAs are components of the ribosome and are essential to the process of translation. RNA polymerase I synthesizes all of the rRNAs except for the 5S rRNA molecule. The “S” designation applies to “Svedberg” units, a nonadditive value that characterizes the speed at which a particle sediments during centrifugation.

Locations, Products, and Sensitivities of the Three Eukaryotic RNA Polymerases
RNA Polymerase Cellular Compartment Product of Transcription α-Amanitin Sensitivity
I Nucleolus All rRNAs except 5S rRNA Insensitive
II Nucleus All protein-coding nuclear pre-mRNAs Extremely sensitive
III Nucleus 5S rRNA, tRNAs, and small nuclear RNAs Moderately sensitive

RNA polymerase II is located in the nucleus and synthesizes all protein-coding nuclear pre-mRNAs. Eukaryotic pre-mRNAs undergo extensive processing after transcription but before translation. For clarity, this module’s discussion of transcription and translation in eukaryotes will use the term “mRNAs” to describe only the mature, processed molecules that are ready to be translated. RNA polymerase II is responsible for transcribing the overwhelming majority of eukaryotic genes.

RNA polymerase III is also located in the nucleus. This polymerase transcribes a variety of structural RNAs that includes the 5S pre-rRNA, transfer pre-RNAs (pre-tRNAs), and small nuclear pre- RNAs . The tRNAs have a critical role in translation; they serve as the adaptor molecules between the mRNA template and the growing polypeptide chain. Small nuclear RNAs have a variety of functions, including “splicing” pre-mRNAs and regulating transcription factors.

Questions & Answers

What's the function of epiglottis
Ugo Reply
What Is The Other Name For Intestinal Juice?
Justin Reply
what is the largestest planet of the universe
rick Reply
what are the types of cell
Bernard Reply
prokaryotic and eukaryotic
Yazi
prokaryotic cell and eukaryotic cell
Grace
what is the protein found in the blood?
Tobias Reply
globin
Joelia
Globin
globulins
EZRA
globulins
SASMITA
globulins
Grace
what is parasitic movement
Emmanuel Reply
Parasitic movement is a problem for all of us. So is its companion, parasitic tension. Parasitic movement is the excess contraction of muscles that you don't actually need to complete an action.
freya
HW a u
Nyandera
cool
Bigenis
am OK how a u
Ocen
absorption may simply mean utilization of food in the body
Bigenis
what are eukaryotic cells
Thiza Reply
eukaryotic cells which posses a true nucleus that is the DNA is enclosed and covered by a nuclear membrane
Grace
what is the mean of pair of chromosomes
Kazula Reply
hi
Lagos
23 haploid and 23diploid
Patson
how are you studying in this quarantine? .. how are you keeping yourselves motivated?
sivajijadhav @815.com
good morning guyz
Joelia
morning
Kazula
hi
Justin
Good
Angela
tell me if you know what can be used...than reading pls hint me pls 🙏🙏🙏
Angela
what is the important of sex
Aremu Reply
why did human being need sex?
Aremu
because he/she have feelings
Chripine
reproduction...to make more
Yazi
due to active harmon
Manish
One important of sex is to reproduce
Emma
to ensure the countinuty of life
Yusuf
all of you are right
Edith
for sexual satisfaction and birth
Grace
what is momentum
Asiya Reply
The strength or force that allows something to continue or grow stronger or faster as time pass
Emma
What is Centripetal Force?
Justin
centrepital force is the inward force required to keep a body moving with constant speed in a circular path
Yusuf
what is the test for protein
Takii Reply
List four condition necessary for seed germination
Tedeka Reply
water,air(oxygen),light,temperature
Hassan
water, light, oxygen and temperature
lilchris
water, oxygen, light temperature
Mike
water oxygen light and temperature
John
importance of biology
Alabina Reply
importance of boilogy
Alabina
what is soil
Amina Reply
soil is the upper part of the earth
Alabina
what is importance of studying biology
Alabina
soil is the uppermost layer of the earth on which plant grows
Yusuf
soil is defined as the thin surface of the upper most layer of the earth crust on which plants grow
Thanni
soil is the upper part of the earth which plants grow on
Emma
soil is the uppermost layer of the earth in which most of the necessary nutrient are found and serve as habitats for some organisms
Grace
soil is the uppermost layer of the earth in which most of the necessary nutrients are found and serve as habitats for some organisms
Grace
soil is the uppermost layer of the earth in which most of the necessary nutrient are found and serve as habitats for some organisms
Grace
soil is the uppermost layer of the earth in which most of the necessary nutrients are found and serve as habitats for some organisms
Grace
soil is the accumulation of lose weathered materials which covers much of the land surface of the earth
rick

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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