Transription and RNA and miRNA Flashcards
What is meant by Gene Expression?
DNA -> RNA -> protein.
What types of RNA are there? Which enzymes make them? What other proteins are involved?
mRNA is made by RNA polymerase II
tRNA, sRNA are made by Pol III
rRNA is made by Pol I
Transcription factors and initiation proteins
What is the basal Transcription complex? how does it assemble? Why?
The BTC is the complex to start transcription (brings RNA pol to TATA site). Starts with TFIID bindin TATA (and unwind it). then TFIIA and B bind, and B binds RNA pol and TFIIF. Finally TFIIE, F, H and J bind.
Absence of BTC leads to low transcription
How about transcription factors? what factor they play?
They bind upstream or downstream of the TATA box and can “Bend DNA” and interact with the BTC, modulating transciption
What are some roles of TF?
Some can work on histone methylation and acetylation (closing and opening histone to allow acess)
Why are TF important and studied? are TF found everywhere?
TF are important because their regulation of transcription leads to specific expression in differetn tissues. In each tissue, specific cocktails of TF can lead to differential expression, which creates different tissues (can control GF, hormones, heat response, cell singalling etc)
Can TF mutation lead to disease? which ones?
YEs mutation are found in several cancers-and some descbribed specifically. Over half of leukemias are TF related (remeber BCR-ABL). Same with oestrogen receptor in breats cancer-which is directly a receptor and a TF-over expressesion leads to cancer
What is the mechanism of action of Aspirin?
Asprin acts of NFkB and IkB, which regulate inflamation response. Stops breakdown of IkB (which released NFkB) which leads to inflamation to be stopped (never transcribe factors
How does transcription work in E.coli?
Only 1 RNA polymerase-heterodimer of a and B subunit. Sigma factor binds and recognises TATAAA, and brings polymerase into it-> starts transcription. can be inhibited by some antibiotics
What is RNA processing?
The combination of processes that transform the primary transcript/ Pre-mRNA into functional mRNA that can be read
What are the 3 main parts of RNA processing?
Splicing, capping and polyadenylation
What is splicing?
In a pre-mRNA, not all is used to make the mRNA. Only yhe exons are kept-while the introns are recycled. At the start of an intron, there is an AGGU-splicing donor. An the end, Pyrrimidinex15 NCAG -exon -splicing donor. snRNPs (small ribonuclear proteins do the splicing. First U1 bind the GG of AGGU. U5 bind the CAG, and U4,U2 and U6 bind the intron. U1 splicing AG I GU, and cycles the GU part back to a branchpoint A, making a U-5’G-2’A (unique). The splicing acceptor site is then cleaved, releasing a lariat. Exon are finally joined
What is capping?
The 5’ end of the mRNA gets modified with a GTP linked to the triphosphate 5’ end. The GTP is futher modified to be methylated, creating a 7meGppp cap (which links 5’ C to 5’ C)
What is polyadenylation?
adding an A tail after the mRNA-can be 10 to lots long. Helps stability.
