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Lecture 4

BIOLOGY 1A03 Lecture Notes - Lecture 4: Astrocyte, Chromatin, Growth Factor

Course Code
Lovaye Kajiura

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McMaster 2018 Weblinks Project
Stephanie Wang
March 9th, 2018

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DNA polymerase IV primarily operates outside of DNA replication forks in Escherichia coli
In E. coli, damage to chromosomal DNA induces an emergency response, paving the road for
DNA repair and damage tolerance reactions. Polymerase IV stalls damaged DNA templates and
other substrates, including single-stranded DNA gaps etc. This study visualizes fluoro-labelled
pol IV in live cells, then treat them with DNA damaging antibiotic/ or UV light to measure
changes in pol IV concentration and location through time. The study showed a result that the
pol IV carries our non-relisomal functions. Pol IV acts at sites away from replisome such as
single stranded gaps left behind by DMA poly III.
Useful to Bio 1A03 because we learn about polymerase I, II, and III, but we rarely think about
the other mechanisms behind DNA replication, and how cells repair DNA damage. This
research in E. coli will help current students take their knowledge further, and apply DNA
replication and repair to real-life examples. This experiment used a technique already discussed
in class, and is easy (relatively) to understand. This disproved a huge misconception that Pol IV
interferes with Pol III, but that isn’t the case. Pol IV interacts remotely, away from the replisome.
Diverse molecular choreography of replication
Complex molecular assemblies are required for the duplication of DNA transmission of genetic
information to the next generations. Cellular DNA replication factories depend on ring-shaped
hexameric helicases. They help DNA synthesis by unzipping parental DNA helix. The molecular
choreography of DNA replication initiation is diverse across organisms, so there are many
different strategies that prepare replication.
This can help Bio 1A03 students learn about more ways that DNA replicates itself. Eukaryotic
and prokaryotic cells go through the same process although the choreography of DNA
replication initiation is very different across systems. This can help students understand that
even though prokaryotic and eukaryotic DNA replication is different, the two processes are also
similar in some ways.
Impaired DNA replication derepresses chromatin and generates a transgenerationally inherited
epigenetic memory
Impaired DNA replication is the cause of cancer and genomic instability. Impaired DNA
replication during embryonic development has major epigenetic consequences for a genome
and individual. Impaired DNA replication in embryos are lacking histone modifications in
combination. Impaired DNA replication has major directional epigenetic impacts on a genome.
This includes loss of heterochromatic histone modifications, increased levels of euchromatic
modifications and increased expression from many normal heterochromatic genes. This is
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