1 / 17

Controlling Chromatin Structure

Controlling Chromatin Structure. Chapter 30. 30.2 Chromatin Can Have Alternative States. Chromatin structure: is stable cannot be changed by altering the equilibrium of transcription factors and histones. Figure 30.2. 30.3 Chromatin Remodeling Is an Active Process.

moeshe
Télécharger la présentation

Controlling Chromatin Structure

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Controlling Chromatin Structure Chapter 30

  2. 30.2 Chromatin Can Have Alternative States • Chromatin structure: • is stable • cannot be changed by altering the equilibrium of transcription factors and histones Figure 30.2

  3. 30.3 Chromatin Remodeling Is an Active Process • There are several chromatin remodeling complexes that use energy provided by hydrolysis of ATP. Figure 30.3

  4. The SWI/SNF, RSC, and NURF complexes all: • are very large • they share some common subunits • A remodeling complex does not itself have specificity for any particular target site. • It must be recruited by a component of the transcription apparatus. Figure 30.5

  5. 30.4 Nucleosome Organization May Be Changed at the Promoter • Remodeling complexes are recruited to promoters by sequence-specific activators. • The factor may be released once the remodeling complex has bound. Figure 30.6

  6. The MMTV promoter requires a change in rotational positioning of a nucleosome to allow an activator to bind to DNA on the nucleosome. Figure 30.7

  7. 30.5 Histone Modification Is a Key Event • Histones are modified by: • methylation • acetylation • phosphorylation Figure 30.8

  8. 30.6 Histone Acetylation Occurs in Two Circumstances • Histone acetylation occurs transiently at replication. Figure 30.12

  9. Histone acetylation is associated with activation of gene expression. Figure 30.13

  10. 30.7 Acetylases Are Associated with Activators • Deacetylated chromatin may have a more condensed structure. • Transcription activators are associated with histone acetylase activities in large complexes. Figure 30.14

  11. Histone acetylases vary in their target specificity. • Acetylation could affect transcription in a quantitative or qualitative way.

  12. 30.8 Deacetylases Are Associated with Repressors • Deacetylation is associated with repression of gene activity. • Deacetylases are present in complexes with repressor activity. Figure 30.16

  13. 30.9 Methylation of Histones and DNA Is Connected • Methylation of both DNA and histones is a feature of inactive chromatin. • The two types of methylation event may be connected.

  14. 30.10 Chromatin States Are Interconverted by Modification • Acetylation of histones is associated with gene activation. • Methylation of DNA and of histones is associated with heterochromatin. Figure 30.17

  15. 30.11 Promoter Activation Involves an Ordered Series of Events • The remodeling complex may recruit the acetylating complex. • Acetylation of histones may be the event that maintains the complex in the activated state. Figure 30.18

  16. 30.12 Histone Phosphorylation Affects Chromatin Structure • At least two histones are targets for phosphorylation, possibly with opposing effects.

  17. 30.13 Some Common Motifs Are Found in Proteins That Modify Chromatin • The chromo domain is found in several chromatin proteins that have either activating or repressing effects on gene expression. • The SET domain is part of the catalytic site of protein methyltransferases. • The bromo domain: • is found in a variety of proteins that interact with chromatin • is used to recognize acetylated sites on histones.

More Related