Eukaryotic transcription

ByG.PRANAVATHIYANI

B.Sc BIOINFORMATICS

Prokaryotes - Transcription - cytoplasm.Translation - cytoplasm.

Eukaryotes - transcription - cell's nucleus. mRNA →cytoplasm→ Translation.

•DNA in prokaryotes - 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 - chromatin.

Difference between prokaryotic and eukaryotic transcription

•While RNA polymerase interacts directly with prokaryotic DNA, other proteins mediate the interaction 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.

A promoter is a region of DNA that initiates transcription of a particular gene

A terminator, or transcription terminator is a section of genetic sequence that marks the end of a gene or operon on genomic DNA for transcription

In eukaryotes, terminators are recognized by protein factors and termination is followed by polyadenylation.

An enhancer is a short region of DNA that can be bound with proteins to enhance transcription levels of genes in a gene cluster.

 A silencer is a DNA sequence capable of binding transcription regulation factors, called repressors.

Name Transcribed Product

RNA Polymerase I (Pol I, Pol A) nucleolus Larger ribosomal RNA

(rRNA) (28S, 18S, 5.8S)

RNA Polymerase II (Pol II, Pol B) nucleus

messenger RNA (mRNA) and most small nuclear RNAs (snRNAs)

RNA Polymerase III (Pol III, Pol C)

nucleus (and possibly the nucleolus-nucleoplasm interface)

transfer RNA (tRNA) and other small RNAs (including the small 5S rRNA)

Eukaryotes have three nuclear RNA polymerases, each with distinct roles and properties

Steps in Eukaryotic transcription

Pre-InitiationInitiationElongationTerminationProcessing of RNA

Transcription

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