Eukaryotic Gene Regulation

Many features of gene regulation are common to both bacterial and eukaryotic cells. For example, in both types of cells, DNA-binding proteins influence the ability of RNA polymerase to initiate transcription. However, there are also some differences, although these differences are often a matter of degree. First, eukaryotic genes are not organized into operons and are rarely transcribed together into a single mRNA molecule; instead, each structural gene typically has its own promoter and is transcribed separately. Second, chromatin structure affects gene expression in eukaryotic cells; DNA must unwind

Antiterminator present

RNA polymerase

Antiterminator

Long mRNA

Terminator I

Terminator 2

Antiterminator present

RNA polymerase

Terminator I

RNA polymerase reads through terminator 1...

.and transcribes a longer mRNA.

.that codes for proteins A and B.

Antiterminator

Long mRNA

RNA polymerase reads through terminator 1...

.and transcribes a longer mRNA.

.that codes for proteins A and B.

Antiterminator absent

RNA polymerase

Terminator I Terminator 2 Gene A / Gene B /

Si Promotern

16.19 Antiterminator proteins bind to RNA polymerase and alter its structure so that it ignores certain terminators.

Transcription

Short mRNA

Translation

i

Protein A

Transcription

RNA polymerase stops at terminator 1.

A short mRNA is produced that codes for protein A.

RNA polymerase stops at terminator 1.

A short mRNA is produced that codes for protein A.

from the histone proteins before transcription can take place. Third, although both repressors and activators function in eukaryotic and bacterial gene regulation, activators seem to be more common in eukaryotic cells. Finally, the regulation of gene expression in eukaryotic cells is characterized by a greater diversity of mechanisms that act at different points in the transfer of information from DNA to protein.

Eukaryotic gene regulation is less well understood than bacterial regulation, partly owing to the larger genomes in eukaryotes, their greater sequence complexity, and the difficulty of isolating and manipulating mutations that can be used in the study of gene regulation. Nevertheless, great advances in our understanding of the regulation of eukary-otic genes have been made in recent years, and eukaryotic regulation continues to be one of the cutting-edge areas of research in genetics.

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