BIOL 483 Lecture Notes - Lecture 13: Hepatocyte, Chromatin, Heterochromatin
Document Summary
H3k9me3 & h3k27me3 similarities: can repress silent genes. 2) transcriptional silence: have positions that differ between cell types. H3k9me3 prevents binding by tfs and rna pol 2. > more restrictive, barrier to cell fate control. H3k27me3 allows binding by tfs and rna pol2. > less restrictive, allows for binding by many factors. These lysines are on different positions on histone tails laid down by 2 different enzymes. > functional differences between modification sites on h3 tail. Polycomb repressive complex = 2 forms of enzymes that methylated h3k27, put down mark and allow mark to recruit other factors for chromatin compaction. Nucleosome prevents transcription initiation, need open sites for polymerase to enter to bind in nucleosome. Longer repeat lengths at linker histone means more compact. Once rna pol starts chugging, it can penetrate nucleosome -> nucleosome partially unwrapped. Mapping h3k9me3 heterochromatin in development to see how dynamic the mark is.
