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Lecture 4

Lecture 4 Eukaryotic Gene Regulation

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Darrel Desveaux

Lecture 4 Text Notes Gene Transcription and Regulation - main features of eukaryotic gene regulation that are different from bacteria: • eukaryotic RNA polymerase II (transcribes all protein-coding genes) requires five general transcription factors – bacterial RNAp only needs one (the σ subunit) • stepwise assembly of the general transcription factors at a eukaryotic promoter provides multiple steps at which the cell can speed up or slow down the rate of transcription initiation (in response to gene regulatory proteins) • eukaryotic cells lack operons (sets of related genes transcribed as a unit) and must regulate each gene individually • each bacterial gene is controlled by one or only a few gene regulatory proteins – common for eukaryotic genes to be controlled by many (complexity is possible because many regulatory proteins act over very large distances along DNA) • central to eukaryotic gene regulation is Mediator (24-subunit complex that is an intermediary between gene regulatory proteins and RNAp) • Mediator provides an extended contact area for gene regulatory proteins compared to that provided by RNAp alone (as with bacteria) • packaging eukaryotic DNA into chromatin provides many opportunities for transcriptional regulation – not the case in bacteria - gene control region – area of DNA involved in regulating and initiating transcription of a gene - promoter – spot where general transcription factors and polymerase assemble - regulatory sequences – serve as binding sites for gene regulatory proteins in order to control the rate of the assembly at the promoter - regulatory sequences can be spread over long stretches of DNA, even up to 50k nucleotides - small number of gene transcription factors (but abundant on promoters of all genes transcribed by RNAp II) - regulatory proteins – presence on DNA affects the rate of transcription initiations - large number of different gene regulatory proteins (thousands) - about 2k genes encode f
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