Flashcards in 1-45 Eukaryotic Transcription II Deck (58)
mRNA processing in eukaryotes includes...
where/when do these occur?
3' polyadenylation (poly-a-tail)
occur in nucleus before shipment to ribosome
and three functions?
7-methylgunaosine nucleotide added to 5' end of pre-mRNA.
1. protects mRNA from degredation
3. allow translation by ribosome
where does it occur
100+ nucleotides added to 3' end of the pre-mRNA
occurs past the poly (A) addition signal. Provides same benefits as 5'cap
alternative splicing patterns allow for..
intron sequences in pre-mRNA are spliced out, leaving exons
allows for multiple distinct protein products from a single transcribed DNA sequence
mutations involving the splicing process can lead to..
progeria - RNA splicing disease
-mutation in area coding for nuclear lamina creates false splice site, more genetic material is spliced out of mRNA than desired
drugs targeting the splicing process have...
proven effective against diseases such as Spinal Muscular ATrophy
-drug dislodges the splicing repressor for that exon
non-coding RNA's can regulate..
microRNA (miRNA) and gene expression regulation
along with RISC proteins, small RNA sequences base pair match with mRNA's and either inhibit or degrade translation
small interfering RNA (siRNA) and gene expression regulation
cleave target mRNA's
piRNA (Piwi-Interacting RNA) and gene expression regulation
prevention of transposition of transposons in the germline
lncRNA (Long Non-Coding RNA) and gene expression regulation
Engage in RNA-RNA, RNA-DNA, and RNA-protein interactions to regulate
is becoming the method of choice for certain diagnoses
detects types/amounts of RNA sequences present in given cell types
eQTL's - expresision quantitative trait loci take this idea and apply it to disease diagnosis - certian profiles of mRNA expression in certain tissues are associated with diseases
expresision quantitative trait loci apply RNA sequencing and apply it to diagnosing diseases - certain profiles of mRNA expression in certain tissues are associated with diseases
encyclopedia of DNA elements aims to map epigenetic sites in the genome and properties of those histones including
• Transcription factor binding sites
• cis-acting enhancers
• Nucleosome positioning
• Histone modifications
• RNA splicing signals
• Non-coding RNA’s
• Chromosome looping interactions
• Replication origins
recent nobel prize-winning studies have shown that..
differentiated cells can be reprogrammed back into stem cell state OR directly into other kinds of differentiated cells using a few transcription factors
RNA interference, two types
1. a perfect base match will recruit factors to destroy the mRNA
2. a near-perfect base match will recruit inhibitory factors
Many gene activator proteins are comprised of an "activation domain" which is separate from a DNA-binding domain. TF
A 2'-5' phosphodiester bond is formed in which of the following processes:
RNA splicing. G cap
what is the enzyme/protein required for recognition of the TATA box by the RNA polymerase II transcriptional machinery.
TFIID -factor specific for binding to the TATA box; one of its subunits is TBP- TATA-binding protein.
enzyme/protein directly required for gene expression by unpacking DNA in nucleosomes.
HAT enzymes activate transcription by aceytylating nucleosomes, reducing their positive charge and thereby their hold on DNA wrapped around them, thereby exposing nucleotide sequences such as the TATA box for protein binding (in this case by TBP, which initiates the cascade of binding by general transcription factors for ultimate binding by PolII).
guanyl transferase methyl trasnferase
puts '5 G cap on backwards in 5'-5' linkage
poly A polymerase adds
adenisines at 3' tail
alternative splicing allows...
a single gene to generate different isoforms of teh same proteins. Important because we have fewer genes than a housefly, but we do more splicing.
a big gene is more likely to...
recombine with its homologue than a small gene.
this helps create diversity
the sequences required for intron removal
donor, acceptor, and branchpoint are cis-acting sequences
way to cure spinal muscular atrophy?
in normal neurons, functional SMN1 and nonfucnctional SMN2 are spliced differently, leading to their differential functionalities
In SMA, the SMN1 splicing pattern is lost due to a mutation, and the only splcing pattern available (SMN2) creates unstable proteins only.
the idea is to change the splicing of SMN2 RNA to the splciing pattern of SMN1 with drug therapies
how do SMA drugs work?
prevent binding of "splicing repressors" which prevent exon 7 of 6-7-8 from being spliced out like in the SMN2 splice pattern
U1 snRNP binds to 5' splice site
U2 binds near 3' splice site
these come together, loop out, and cut out the extraneous introns.
the resulting loop of introns
lariat biology is being pursued for the treatment of..
functions of RNAi
some genes downregulated by transcribing small RNA's that are complementary to the RNA's you want to destroy
ssRNA forms complex that targets RNA by way of complementarity. Small RNA base pairs with target RNA and brings along regulatory complex to destoy it
2 ways that RNAi can inhibit
destroy given mRNA or inhibit translation without destroying it
miRNAs and siRNAS form distinct..
complexes and downregulate mRNA by distinct mechanisms
what do miRNA's do?
they are mostly base paired, repress translation
what do siRNA's do?
perfectly base paired, cleaves target RNAs
what is "IncRNa's can act in cis or trans" mean?
long non coding rna's can work in cis by regulating genes nearby, or in trans by regulating genes far away.
expresssion quantitative trait loci
you can use expression level of agene as a marker like any other marker
-compare expression level of mRNAS in normal vs diseased using RNA-sequenceing
may see that some expression patters are related to certain diseases
eqtl's are tissue
specific...wont get overexpression of liver cells in kidney
eqtl's are heritable. TF
heritable, you can track high expression of a gene through a pedigree like any marker
splicing occurs via ___ acting sequences
relative amount of coding and non coding RNA?
non coding RNA outnumber, important regulatory functions
small noncoding vs large noncoding strategy
lnc - large, bigger, more complex, and can do more. act as scaffolds to assemble protein complexes and take them to particular locations. can work cis or trans
small noncoding target RNA by complementarity
2 ways you can inhibit RNA.
with siRNA's - perfectly base paired, recruits desctuction complex
with miRNA's - mostly base paired, recruits complex to block translation and condense
cis vs trans interaction
cis - RNA made works right next door
trans - rna made on one crhomsome works on distant chromsome
microarrays vs RNA-seq
rely on having to put specific gene probes that you already know are important. must already know the gene that is important.
-only measures the RNAs whose genes you have put on the array
Rna-seq - blind method where you look at everything. measures ALL rnas in the cell
what do microarrays tell you
compare expression of normal tissue genes and diseased genes. must know what genes to use (a.priori knowledge)
will become method of choice - way to sequency and quantify total RNA in the cell. entire genome, including non-coding
advantage of SNP's vs eQTLs?
eQTL's are tissue specific, SNPS are in every cell.
eQTL's may indicate a function in that particular tissue. may also help insignt into disease by discovering tissue specific eQTLs
2 uses of IPS cells
induced pluripotent stem cells
-disease modeling - mimic condition of the disease on cells to try drugs
-treatment - take own cells, convert to IPS cells and then heathyl speicalized cells, and put back into body
gene regulation relies on
expression of cell type and gene specific trasncription factors
AND non-coding RNa's
describe transcription factors
modular and bind to specific enhancers
transcription factors help recruit
RNA pol II or enzymes that modify chromatin structure/chemistry
cells can be reprogrammed by
transcription factors, as few as four, for therapeutic potential
D. Gene activator proteins may function by either
recruiting the transcriptional machinery to the promoter or by changing chromatin structure around the promoter.
How do HAT activate transcription?
HAT enzymes activate transcription by aceytylating nucleosomes, reducing their positive charge and thereby their hold on DNA wrapped around them, thereby exposing nucleotide sequences such as the TATA box for protein binding
TBP does what?
it is a subunit of TFIID, reponsbible for TFIID binding to the TATA box
TBP = tata binding protein
describe eQTL specificity
whole blood and lymphoid cells had strong eQTLs for autoimmune diseases (chrohns) consistent with these tissues being involved. In contast, blood did not show eQTL's for bipolar disorder or type 2 diabetes.