BIOL 142 Lecture Notes - Lecture 23: Prokaryote, Chromatin Remodeling, Natural Selection
Biology'142-'Lecture'23-'Eukaryotic'Gene'Regulation'and'Evolution'
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Transcription'is'controlled'by'the'interaction'of'regulatory'proteins'with'variable'regulatory'
elements!
• DNA!->!methylated!->!closed!state!!
• DNA!->!acylation!->!open!state!!
• All!eukaryotic!genes!have!a!common!promoter!and!variable!regulatory!elements!
o All!eukaryotic!promoters!are!bound!by!the!TATA-binding!protein!at!the!TATA!box!
o Occurs!at!the!beginning!of!the!gene!and!is!the!site!where!RNA!polymerase!begins!
transcription!
o Downstream!is!the!gene!itself!(made!of!exonerated!and!introns)!
o Promoter-proximal!elements!are!upstream!of!promoter,!and!have!unique!
specific!genes!
§ Pro-transcription,!have!regulatory!effects!on!the!gene!
• Eukaryotic!genes!have!enhancers!and!positive!regulatory!control!elements!
o Enhancers!can!be!100,000!or!more!bases!from!the!promoter,!in!introns,!or!5’!to!
3’!flanking!sequences!
§ Different!enhancers!are!associated!with!different!genes!
§ Activator!proteins!bind!enhancers!and!strongly!stimulate!transcription!
complex!
§ There!can!be!many!different!enhancers!
o Silencers!are!negative!control!element,!and!repress!rather!than!activate!
expression!!!
§ Silencers!bind!proteins!(“repressors”)!and!turn!off!expression!!
§ Note:!these!are!similar!to!the!operators!in!prokaryotic!cells!
• Basal!transcription!factors:!the!bare!minimum!needed!to!do!transcription!(ex.!RNA!
polymerase)!
• Different!cell!types!express!different!genes!because!they!contain!different!regulatory!
proteins!
o Extracellular!signals!trigger!cell-specific!gene!expression!
o Activation!of!specific!regulatory!proteins!by!extracellular!signals!leads!to!certain!
proteins!being!provided!only!in!certain!types!of!cells!
!
Classes'of'proteins'that'bind'to'regulatory'sequences'of'eukaryotic'genes'
• Basal!transcription!factors!!
o They!interact!with!the!promoter!and!are!not!restricted!to!particular!cell!types!!
o Required!for!transcription,!but!do!not!regulate!gene!expression!
o Example:!RNA!Polymerase!
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Document Summary
Biology 142- lecture 23- eukaryotic gene regulation and evolution. Pro-transcription, have regulatory effects on the gene: eukaryotic genes have enhancers and positive regulatory control elements, enhancers can be 100,000 or more bases from the promoter, in introns, or 5" to. Different enhancers are associated with different genes. Activator proteins bind enhancers and strongly stimulate transcription complex. There can be many different enhancers: silencers are negative control element, and repress rather than activate expression. Silencers bind proteins ( repressors ) and turn off expression. Note: these are similar to the operators in prokaryotic cells: basal transcription factors: the bare minimum needed to do transcription (ex. Rna processing: rna splicing is a form of transcriptional control, alternative splicing of specific pre-mrna can generate different protein from a single gene. Evolution: evolution is a change in heritable traits of biological populations over successive generations.
