theme 2- CB14 Flashcards
How is transcription initiated for most proteins?
1) A general transcription factor (TFIID) binds to the TATA box. 2) The binding causes a distortion in the structure of the DNA. 3) Now other factors can assemble along with RNA Polymerase 2. = transcription initiation complex 4) RNA polymerase’s “tail” is phosphorylated by TFIIH, this helps polymerase disengage from the cluster of transcription factors = TFs released &transcription begins
What is the TATA box?
(composed mostly of adenine and thymine bases, its a key component of the promoter region)
Is the transcription initiation complex formed at all gene promoters?
no but most of them
Why is gene transcription regulated?
-to achieve differences in gene expression between cells to allow for cell diversity and development -some proteins are required in larger quantities, regulation allows the rate of gene transcription to not be regulated
Names the 7 steps eukaryotic gene expression is controlled:
7) being the control of degradation of protein
What are the different ways transciption factors can functions?
1) activate or repress the formation of the transciption initiation complex by either attracting or repelling the RNA polymerase& general transsciptor factors to the promoter after binding to the enhancer region.
2) Altering the strucure of the chromatin changing the level of accesibility
- by chromatin-remodelling complexes attaching to transciption regulator = remodelled nucleosomes= TATA box more accessible
- by using enzeymes that covalently modify histone proteins e.g. histone acetylase= add acetyl group= descreases DNA and histone association= less tightly coiled= < accesibility
+ acetyl groups are recoginised by proteins that promote transciption,e.g. some general transciption factors
Name areas where u find repressed genes due to compact DNA:
1) Large swathes: Heterochromatin found in interphase chromosomes, X chromosome in female mammals
2) single gene silenced: genes where the enhancer region has been bound to by a repressor protein which has caused tight packing of nucleosomes by using a certain chromatin-remodelling complex or histone-modifying enzeyme
What is the charge of DNA?
Phosphate groups which are negatively charged and give DNA molecules a negative charge
What amino acid is actylysed in histones?
What is the effect?
1) lysine
2) removes the charge of the R group= no interaction with negatively charged DNA= DNA-Histone complexes less tightly packed= more accesible for general TF and RPII
1) What enzeyme does an activator protein have if it covently modifies the histones?
2) What enzeyme does an repressor protein have if it covently modifies the histones?
3) How can bacteria modify host transcription activity?
1) histone acetyltransferase
2) histone deacetylase
3) by producing histone deacetylase activity (HDAC) repressors= host can’t prevent transcription of a gene
1) How many RNA polymerases are there
2) Where does RNA polymerase bind?
3) How is transciption initiiated?
a) In prokaryotes b)in Eukaryotes
1) a)single RNA Polymerase b)3 RNA polymerase, RPII transcribes most genes
2) a) b) promoter sequence immediatly upstream of gene (b)in the case of RPII
3) a) RP can initiate transcription with the help of a single factor ) b)RPII requires help from the assembly of (general) transcription factors at the promoter
4) Describe complexity of controlling transciption and why?
5) Describe the regulatory DNA sequences that regulate gene transciption:
6) describe the layers of structure of DNA:
a) In prokaryotes b)in Eukaryotes
4) a) simple due to genome structure, b)complex, genes spead in genome, many regulatory elements in addition to promoter
5) a) simple &short, switch transcription on &off, b) long &complex, acts as microprocessors regulating gene transcription
6) 1) single DNA strand, no histones so no higher orders structures, B)Mutiple chromosomes, histones, complex and dynamic higher order structure
What line of enquiry is modern medicine going into with HDAC inhibitors?
use as an anticancer agent for it inhibits HDACs and carrys out significant antitumor activity in several human malignancies, including oral squamous cell carcinoma (OSCC).
What are the two types of transcription factors?
1) general TF
2) gene regulatory proteins (transcription regulators/factors that are tissue specific or inducible proteins)
What are regulatory genes?
enhancers and promoters
