Lecture27 - System Biology: Definitions Lecture 27: Systems...

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Lecture 27: Systems Biology and Bayesian Networks § Systems Biology and Regulatory Networks • Definitions • Network motifs • Examples § Bayesian Networks • Bayesian Statistics • Bayesian Networks System Biology: Definitions § Nodes (circles): Genes/Proteins § Edges (lines): interactions § Edges can represent: • protein-protein interactions • protein-DNA interactions (e.g. TF binding to promoter) • genetic interactions • regulatory or functional interactions § Edges can have directionality (gene X regulates gene Y) § Edges can represent positive or negative regulation Protein-protein interaction Activator Target Repressor Target Image from Alon (2007) Nat Rev Genet. 8:450-61 Transcription Factor Autoregulation § Transcription factors (TF) frequently bind to their own promoters and regulate their own transcription § Which network would respond more rapidly (by increasing the expression of the TF protein) in response to a signal? Negative Autoregulation Positive Autoregulation No Autoregulation Negative None Positive TF TF TF Transcription Factor Autoregulation § Negative autoregulation facilitates a more rapid response to a signal § Positive autoregulation delays gene expression in response to a singal Negative Autoregulation Positive Autoregulation TF TF No Autoregulation TF Negative None Positive Image from Alon (2007) Nat Rev Genet. 8:450-61
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Transcription Factor Autoregulation: Summary § Negative autoregulation facilitates a more rapid response to an environmental signal § Positive autoregulation delays gene expression in response to an environmental signal § Negative autoregulation helps maintain the expression of the TF at a constant level § Positive autoregulation can cause bistability Negative Autoregulation Positive Autoregulation TF TF Complex Network Motifs: Feed-Forward Loops § Some network motifs are very common in biological networks (over-represented)
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This note was uploaded on 01/20/2012 for the course MBIOS 478 taught by Professor Staff during the Fall '11 term at Washington State University .

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Lecture27 - System Biology: Definitions Lecture 27: Systems...

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