Eukaryotic Gene Regulation

Chapter 18 & 20

Goals:

• Gene Regulation in Eukaryotes– Regulation at the DNA Level– Regulation at the transcription level– Regulation at the translation level– Regulation at the protein level

– How might regulation change the function of a stem cell? Cause a cell to become cancerous?

Central Dogma in Eukaryotes• Transcription and Translation are separated!

DNA Level Control• What does histone acetylation do?• What does DNA methylation do?

RNA Level Control (Transcription)

• Transcription Factors• Alternative Splicing• Cap and Tail

Transcription factors• Bind enhancer region and promote RNA

polymerase. Make TATA box recognizable!

Alternative Splicing• One gene = many

proteins• Original

hypothesis (Beadle and Tatum)=one gene; one enzyme

• Intron: intervening

• Exon: expressed

Cap and Tail• The RNA transcript must be protected from

DNAses in the cytoplasm!– 5’ GTP cap: protects the end and helps the RNA

bind to the ribosome– 3’ polyA tail: protects the end and allows RNA to

go tail first out of the nucleus

Control of Translation

• RNAi:– Triggered by siRNA’s• dsRNA is chopped up by “dicer”

– Can do two things:• Degrade RNA

– RISC complex leads to chopping up of mRNA• Block Translation

– RISC complex leads to hairpin shape that blocks translation by ribosome.

Dicer’s Role in RNA degredation

Model for translational repression

Further research

• NOVA video: (accelerated biology level)– NOVA, RNAi– http://video.pbs.org/video/1506740590/

• Pdf review from Nature: Available on my website (college level).

Regulation of Gene Expression at the Protein Level

• Activation or inhibition of proteins– Can the timing of when a protein is expressed be

altered? Even if it is present the whole time?– Have we seen this already this year?– Many proteins functon as complexes working

together.• P53 is often one a few transcription factors needed to

activate transcription. Without its “friends” p53 activity is downregulated

p53 and its interaction with other proteins to regulate its activty

How can cancer genes be regulated at the various levels of regulation?

How can embryonic development be regulated at the various levels of regulation?