23 - Transcription (Eukaryotes); Initiation by RNAPII

23 - Transcription (Eukaryotes); Initiation by RNAPII -...

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Unformatted text preview: Core promoter element (e.g. TATA box) Upstream elements Enhancers/silencers Regulatory elements General pattern of regulatory sequences that control gene expression To review what we talked about (cont.): Class II promoters (promoter regions) have two parts Tissue specificity of regulatory (cis) elements DNA is the same in every cell/tissue of the organism the very same cis elements (including enhancers) are present in each tissue Tissue specificity is due to either presence or absence of particular regulatory (=binding) protein(s), also known as transcription factors (TFs) Regulatory proteins are tissue specific Regulatory proteins dictate tissue specificity of cis elements; very important at the level of initiation of transcription Enhancer Promoter Control elements Albumin gene Crystallin gene Liver cell nucleus Lens cell nucleus Available activators Available activators Albumin gene expressed Albumin gene not expressed Crystallin gene not expressed Crystallin gene expressed Liver cell Lens cell Transcription initiation by RNAP II Transcription is highly regulated One gene could be transcribed in response to multiple conditions e.g. heat shock protein(s) - important for cell protection - are expressed when cells are exposed to high temperature AND heavy metals Different conditions are associated with different cis elements which bind different regulatory proteins (transcription factors) Gene that responds to multiple conditions has multiple cis elements (4 in gene A, 3 in gene B) e.g. there are a heat shock response element (HRE) AND metal responsive element (MRE) in promoter regions of genes for heat shock proteins Watson, 5 th edition Certain signal/condition could increase and/or decrease transcription of different genes different genes which respond to the same signal in the same way all have the same cis element (orange element #3 in promoters of genes A and B) There is no consistent location of cis element(s) among different genes (orange element #3 in promoters of genes A and B) In vitro experiments: Cis elements responding to different signals are cloned upstream from a reporter gene cause the reporter gene to be transcribed when particular signal is applied Transcription initiation by RNAP II (cont.) Watson, 5 th edition Promoters are organized to be initiated on principle of mix and match, in other words they are modular Variety of elements can contribute to promoter function (which is to bind RNAP II)- none is essential for (or common to) all promoters in any individual promoter, elements may differ in number, location, orientation (8 bp element) (Lewin, 2006. Fig. 24.18) Summary of modular nature of RNAP II promoters Many have a TATA box as a core element (majority of those that dont - have initiator sequences or CG-islands...
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This note was uploaded on 12/23/2011 for the course BIOL 308 taught by Professor Miskovic during the Fall '09 term at Waterloo.

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23 - Transcription (Eukaryotes); Initiation by RNAPII -...

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