Transcription II Flashcards
what is capping
complex of 3 enzymes form a complex with pol II and modfy the 5’ end of pre-mRNA into a cap
function of cap
allows cell to distinguish mRNA from other types of RNA
spilceosomes
recognize boundaries between exons and introns, catalyze cleavage adn rejioing of RNA molecule
another name for spliceosome
snRNP
what 3 sites are important for splicing to occur
5’ splice site
3’ splice site
branch point w/in intron
splicing reaction
1) adenine residue attacks 5’ splice site, cutting the sufar-phosphate bakcbone
2) 5’ end covalently attachs to adenine nucleotide, making a loop
3) 3’ end reacts with 5’ end of next exon, joing together and releasing intron
functino of splicing
allows more than 1 protein produce to be generated from a single pre-mRNA transcript
differential/alternate splicing
pre-mRNA molecule can be spliced together generating different mRNA molcules
polyadenylation signal
3’ end of RNA specified by DNA signal
function of poly A tail
determinat of mRNA stability
is the poly A tail found elsewhere besides mRNA
no
where does mature mRNA need to go to be transalted
cytoplasm
what governs the stability of an mRNA molcule
its nucleotide sequence
how does degradation of mRNA start
shortening of poly A tail, triggers removal of 5’ cap
what degrades the mRNA molecule from both ends
ribonucleases
how do you get beta-thalassemia
incorrect splicing
symptom of beta-thalassemia
profound anemia
mutation found in PKU patients
single base change in 5’ splice donor site of one particular intron
function of chromatin iremodeling complexes
protein machines tha tuse energy of ATP hydrolysis to change structure of nucleosomes temporailyt so DNA becomes less tightly bound to histone core
how do HATs affect histones
reduce net positive change, decreases strength of their interaction with DNA
affect of HDACs on histones
catalyze removal of acetyl groups from histone. inhibit transcription
what happens when cytosine residues in DNA are methylated
produce 5’ methylcytosine
where do proteins usually bind to DNA
major groove
helix-turn-helix proteins
2 alpha helices conencted by a short chain of amino acids. side changes are important in DNA pbinding
characterisc of zinc finger protein
zinc required for protein folding and function,
alpha helix makes contact with the major groove of DNA
example of zinc finger DNA binding protein
glucocorticoid receptor
leucine zipper protein characteristic
alpha-helix that has a leucine hydrophobic residue protruding down one side.
examples of leucine zipper protein
fos and jun
LDL recptor
glycoprotein that spans plasma membrane
waht does the LDL receptor gene recognize
apolipoprotein B and E
binding of apolipoprotein B or E with LDL receptor gene results in what
endocytosis of receptor
uptake of LDL and VLDL into cell
what is the relationship between LDL receptor gene and cholesteral
it’s icnreased in response to low cellular cholesterol
what happens when you have increased transcription of LDL receptor gene
enchanges cholesterol uptake form blood
what does the promotor of LDL receptor gene have
SRE-1
function of SP-1
help with assemby of pol II and general transciription factors at TATA box
what addition protein does SP-1 need in order to function
CRSP
what is SRE-1 bound to
SREBP-1a
what is SREBP-1a
leucine zipper protein
what happesn to LDL receptor gene when cholesterol levels fall
entery of SREBP-1a into nucleus, where it binds to SRE-1, recruits HAT, relaxes chromaton allowing LDL transcription
what else does SREBP-1a do
binds to promoter regions of genes involved with metabolism of both choelsterol and fatty acids
what is the major glucocorticoid secreted in humans
cortisol
what happens when cortisol binds to glucocorticoid receptor
allows uptake of hormone/receptor complex into nucleus
GRE
where hormone/receptor complex binds, an enchancer element
in most tissues what do thyroid hormones do
stimulate metabolic rate
where are receptors for thyroid hormone found
constituvtively in nucleus
thyroid hormones receptors often bind to DNA as waht
heterodimers
what is the other part of the thyroid hormone dimer
RXR
complex of thyroid recpetor/RXR do what
recruit HDAC activity
what happens when thryoid hormones binds to thyroid receptor/RXR compelx
displacement of HDAC, binding of AHT complex, favors relaxation of chromatine sturucture which facilitates trasncrition
symptom of rubinstein taybi syndrome
intellectual disability, abnormality
what is rubinstein-taybi caused by
point mutations, small deletions and rearrangedment within genes encoding CBP or EP300
tamoxifen
compeititve inhibitor of estrogen receptor, used for breast cancer treatment
