Biology 308- Homework Assignment #5
Due Wednesday October 18th at the start of class (assignments will not be accepted after 8:40AM). Typed hardcopies only. No late copies accepted.
1. Circle each word in Figure 1., and define in your own words. You can use Google, as a resource, but do not copy and paste words from the internet, or from the article.
2. Summarize Figure 1.
3. Use the information from Figure 1 to help you understand Figure 2. If you do not understand words, or terms then perform a Google search.
4. Summarize Figure 2.
5. Since you have now gathered enough information to help you understand the mechanisms of chromatin regulation, below is my question:
What is the role of HATs and HDACs in chromatin remodeling? Would transcription be at basal levels OR upregulated by the absence of HATs or HDACs? What is needed for active and repressed transcription?
Figure 1. Mechanisms of chromatin regulation. Actively transcribed genes are found in open euchromatin and are associated with histone acetylation (H3/H4Kac) and tri-methylation of H3 lysine 4 (H3K4me3) at promotors, and tri-methylation of H3 lysine 36 (H3K36me3) over the gene body. Nucleosome positioning at promoters is regulated by ATP-dependent chromatin remodelers (SWI/SNF). Silenced genes are associated with densely packed heterochromatin marked by DNA methylation (5mC) and H3 lysine 9 tri-methylation (H3K9me3) or in silenced polycomb domains marked by tri-methylation of H3 lysine 27 (H3K27me3). Chromatin modifications are deposited by chromatin modifying enzymes such as DNA methyltransferases (DNMTs), histone acetyl transferases (HATs) or histone methyl transferases (KMTs) and removed by de-modifying enzymes such as histone deacetylases (HDACs) or histone demethylases (KDMs).
Figure 2. Chromatinderegulationin disease. Pathologies can result from changes in gene expression programmes caused by aberrant DNA methylation and histone modification patterns. These changes can be caused by environmental stresses that affect the chromatin state, deregulated expression of wild type (WT) chromatin regulators, or as a result of mutations (either inherited or acquired de novo) in genes encoding chromatin regulatory proteins