Regulation of Gene Expression in Eukaryotes

Genetics BIOL 2004 Kamran Virginia Tech

Do eukaryotes have operons?

NO

What affects access to DNA?

chromatin structure

histone modifications that can alter chromatin structure and give access to DNA

• acetylation —> actiavates transcription

• methylation —> can activate or repress

chromatin remodeling that can give access to DNA

• reposition nucleosomes

• make TFC and RNA polymerase II accessible

DNA methylation

• can block TFC binding

Main takeaway of gene regulation in eukaryotes

DNA has to be unwrapped/accessible for transcription to start

activators

bind enhancers, start transcription

repressors

bind silencers, block activators

enhancers/silencers

• far from promoter

• orientation is dependent

transcriptional stalling

• RNA polymerase pauses

• regulatory factors decide if elongation continues

RNA processing and degradation

post-transcription gene expression regulation

alternative splicing

many protein isoforms from one gene

RNA degredation

• 5’ cap and poly A tail are removed/shortened

• coding sequences or UTRs are degraded

siRNA

• complementary sequence to specific mRNA

• mRNA cleaved where siRNA is bound

miRNA

• partial match with mRNA

• inhibits translation

mechanisms of RNA interference in gene expression regulation

• miRNA

• translation inhibition

• chromatin modification

• RISC carries out actions

regulation at translation/protein level

• availability of chromosomes, charged tRNA, and factors

• protein binding UTRs