Lecture 11 Flashcards
either convert open euchromatin into closed heterochromatin or convert closed heterochromatin into open euchromatin
Chromatin remodeling complexes
1st chromatin remodeling complex to be isolated
SWI/SNF
Example of SWI/SNF complex in euchromatin
HO in yeast
SAGA and SWI/SNF recruitment from SWI5P leads to the…
conversion to euchromatin in the promotor region
Function of SAGA
Adds acetylcholine groups to nucleosomes
Al l repressive chromatin types in mammals are associated with
DNA methylation
When euchormatin converts to Heterochromatin, what is added?
DNA methylation
The slower the dividing organism, the more…
DNA methylation
Once DNA methylation
is established, it can be Maintained by…
Maintenance methylate
Chases DNA polymerase and methylates dna behind it
Methylate
term for a precursor to living cells
Protobiont
consisted of an aggregate of molecules and macromolecules that acquired a
boundary, such as a lipid bilayer
Protobiont
maintained an internal chemical environment distinct from that of its
surroundings
Protobiont
RNA proto-viruses may have used ___ to multiply
lipid bilayer spheres
may have provided an enclosed arena for RNA replication from an RNA template and for protein synthesis
lipid bilayer spheres
Some genes do not encode polypeptides, but are transcribed into
Non coding RNAs (ncRnas)
perform a spectacular array of cellular functions in bacteria, archaea, and eukaryotes
NcRnas
In most cell types, ncRNAs are more abundant than ___
mRNAs
In a typical human cell, only about ___ of transcription involves the
production of mRNAs, whereas ___ of it is associated with making ncRNAs.
20%, 80%
a recently discovered ncRNA that alters chromatin structure
HOTAIR
The HOTAIR gene is located on human chromosome __ within a cluster of genes called the HoxC genes
12
Acts as a scaffold that guides two histone-modifying
complexes to their target genes
HOTAIR
HoxC is controlled by what kind of genes?
Polycomb
transcribed from the opposite (antisense) strand with respect to the HoxC genes
HOTAIR
Conversion of euchromatin to H3K27me3 heterochromatin (a.k.a. Polycomb heterochromatin) requires…
(1) deacetylation
(2) demethylation of H3K4me3 (if present)
(3) methylation at H3K27 to produce H3K27me3
HOTAIR Binds two Protein complexes leading to Transcriptional Repression
Lysine specific demethylase 1 (LSD1) and Polycomb repressive complex 2 (PRC2)
Removes H3K4me3 Which is a euchromatic histone modification
LSD1
methylates H3K27 three times to form H3K27me3
PRC2
Eliminates gene expression
siRNA
RNA Interference, mediated by ____ was found to be a form of gene regulation
microRNAs
are encoded by genes in eukaryotic organisms
MicroRNAs
Give rise to small RNA molecules, typically 21 to 23 nucleotides
microRNAs
are small non-coding RNA molecules (containing about 22 nucleotides) found in plants, animals and some viruses, that functions in RNA silencing and post-transcriptional regulation of gene expression
microRNA
