BIOL 483 Lecture Notes - Lecture 5: Helicase, Dna Replication, Euchromatin
Document Summary
H3. 3 = histone h3 variant linked to replication independent chromatin assembly. Histone h3. 3 deposition coupled to/ incorporated during transcription. People look at h3. 3 levels on dna that have high rna pol occupancy (highly transcribed region), there is high occupancy of this histone at highly transcribed genes. H2a. z incorporation dependent on chr that doubles as a chaperone. Transcription leads to nucleosome loss and incorporation of histone variants mediated by specific chaperones (eg. hira, chr swr1 complex) + at least one h2a-h2b dimer: final state reversed/ reassembly of nucleosome after passage of rna pol, deposition of h3/h4, deposition of h2a/h2b. Chromatin = nucleosomal arrays (genomic dna with properly spaced nucleosomes) Core dna = dna wound around histone octamer. Chromatin remodelers use energy from atp hydrolysis to cause nucleosomal repositioning along chromatin. Dna wrapped around histone octamer to form nucleosomes then compacting nucleosomes into chromosomes is great for packaging dna but restricts genome accessibility. Accessibility is needed for dna replication, transcription, repair.
