Eukaryotic Gene Expression Regulation

Why are eukaryotes capable of regulating gene expression at multiple points?

Why is it essential that the cells of multicellular eukaryotes have a complex and tightly controlled regulatory system?

• DIFFERENTIATION of Individual cells!• Specialized cells must maintain a specific program of gene regulation

DNA Packing: Only Keep necessary genes accessible

• Extensive coiling and folding• Histones: small proteins thatassociate with DNA to form Nucleosomes• Continued folding “supercoil”• This system can block transcription by

preventing RNA polymerase to bind

What is the purpose of adding methyl groups to DNA?

• Marks regions with low or no transcriptional activity (Heterochromatin)

Pre-Transcription

• Regulatory Genes – Produce regulatory proteins (activators and repressors)

• DNA sequences that can activate (enhancers) or inhibit (silencers) transcription

What are transcription factors?

• Any proteins thatMediate the transcriptionProcess• T.F.s bind to specific DNA sequences and/or Other regulatory proteins• Can be activators or repressors

What are transcription factors?

• The combination of T.F.s binding to the Regulatory regions at anyOne time determines howMuch, if any, of the geneProduct will be produced• RNA polymerase cannotBind without T.F.s present

Why is it important that cells of multicellular organisms be able to control the availability of transcription factors in cells?

• This enables cells of multicellular organisms to accomplish “differential gene expression”

• This enables cells to differentiate!

• This is CRUCIAL!!!

Post-Transcription: Alternative Splicing

Pre-Translation: micro RNAs• MiRNAs are producedAfter the transcript for themIs cleaved into multiple Fragments by a dicer protein• miRNAs complex with protein• Any mRNA with a Complementary sequence is “tagged with the miRNA/proteinComplex• mRNA is not translated