BIO SCI 99 Lecture Notes - Lecture 10: Histone Deacetylase, Chromatin Remodeling, Repressor
17 May 2018
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Bio 99 Lecture #4 (part 2)
Lecture based on chapter 21 pages 728 – 752
I. Eukaryotic genomes
a. Increased genetic complexity (more genes, subtler responses)
b. Complex response to environmental cues
c. Multicellular eukaryotes maintain different cell types by differential gene
expression
II. Introduction
a. The transcriptional ground state is the iheet atiit of pootes ad
transcriptional machinery in vivo in the absence of regulatory mechanisms,
and it is not the same in bacteria as it is in eukaryotes
b. I ateia, the tasiptioal goud state is non-restrictive, eaig that
RNA polymerase generally has access to every promoter and can bind and
initiate transcription as some level of efficiency in the absence of activators
and repressors
c. In contrast, eukaryotic genes contain strong promoters that are generally
inactive in the absence of regulatory proteins, meaning that the
transcriptional ground state i eukaotes is restrictive
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2
d. Crucial differences in DNA packaging and cell structure give rise to four
important distinguishing features of regulation of gene expression in
eukaryotes
e. First, access to eukaryotic promoters is restricted by the structure of
chromatin, and transcriptional activation is associated with any changes in
chromatin structure in the transcribed region
f. Second, although eukaryotic cells have both positive and negative regulatory
mechanisms, positive mechanisms predominate in all systems investigated so
far, given that the transcriptional ground state is restrictive, virtually every
eukaryotic gene requires activation
g. Third, eukaryotic cells have larger and more complex, multiprotein regulatory
networks than bacteria
h. Fourth, transcription in the nucleus is separated from translation in the
cytoplasm, both in space and in time
III. Eukaryotic versus prokaryotic gene transcription
a. transcriptional ground state: iheet atiit of poote ad
transcription machinery without activators or repressors
i. Bacterial promoters have a basal (low) transcription rate that can be
turned up or down by activators or repressors
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ii. Eukaryotic promoters are OFF in the absence of regulatory factors
b. Chromosomes are packaged differently
i. Bacterial chromosomes are associated with DNA binding proteins
(polyamines)
ii. Eukaryotic DNA is wound into histone containing nucleosomes
iii. The ople of DNA ad potei pakagig is teed chromatin
iv. Aess to eukaoti pootes egulated chromatin structure:
transcription activation in eukaryotes is associated with local changes
to chromatin structure
IV. Chromatin and transcription
a. An average human chromosome consists of approx. 2 inches of DNA
b. DNA interacts with histones to form chromatin
c. DNA in chromatin is not accessible to transcription machinery
d.
V. Chromatin remodeling allows transcription
a. histoes: asi poteis that pakage ad ode eukaoti DNA ito uits
alled uleosoes
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Document Summary
Lecture based on chapter 21 pages 728 752: eukaryotic genomes, increased genetic complexity (more genes, subtler responses, complex response to environmental cues, multicellular eukaryotes maintain different cell types by differential gene expression. Eukaryotic versus prokaryotic gene transcription: (cid:862)transcriptional ground state(cid:863): i(cid:374)he(cid:396)e(cid:374)t a(cid:272)ti(cid:448)it(cid:455) of p(cid:396)o(cid:373)ote(cid:396) a(cid:374)d transcription machinery without activators or repressors, bacterial promoters have a basal (low) transcription rate that can be turned up or down by activators or repressors. Chromatin and transcription: an average human chromosome consists of approx. 2 inches of dna: dna interacts with histones to form chromatin, dna in chromatin is not accessible to transcription machinery, chromatin remodeling allows transcription, (cid:862)histo(cid:374)es(cid:863): (cid:271)asi(cid:272) p(cid:396)otei(cid:374)s that pa(cid:272)kage a(cid:374)d o(cid:396)de(cid:396) euka(cid:396)(cid:455)oti(cid:272) dna i(cid:374)to u(cid:374)its (cid:272)alled (cid:862)(cid:374)u(cid:272)leoso(cid:373)es(cid:863) 4: steps 2 and 3 progressively induce rna polymerase to dissociate from the. Repression: repressor binding prevents interactions between activators, co-activators, and rna polymerase 2. 12: this interaction cause a conformational change that relieves the inhibition of.
