Week 6B Flashcards
What is the central dogma of molecular biology
Flow of genetic information within a biological system DNA makes RNA which makes protiens
Do all genes encode for protiens
NO some encode for small RNAs miRNA
What do miRNA control
How many protiens are made by other protien-coding genes
What do the effects of miRNA depend on
Presence of mRNA
How do miRNA work
Bind to the complemanry sequence in protiein coding mRNA at the 3’ unstranslated region that either block protien translation or induce mRNA degradation
What is the process of miRNA
Transcribed by RNA pol II as pri-miRNA
THen folds into a hairpin it is usually long in length
endonuclease enzyme Dorsha makes inital cleave and makes pre-mirna
Exportin5 exports premiRNA out of the nucleus into the cytoplasm through difussion
RNAase Dicer processes pre-RNA into a double stranded miRNA
One of the two strands binds to Argonature which is a core protein of the RNA-induced silencing complex RISC
They then associate with the traget MRNA at 3’UTR and either block or degrade
What were miRNA first foun in
neamtode C.elegans encoded by non protien coding genes lin-4 and let-7
What do lin-4 and let-7 regulate
embryogenesis and larval development
Which gene was conserved
let-7
What are characterstics of miRNA
Similar structure of hairpins with imperfect base paring which suggest they can produce different mature miRNA from the same pre-miRNA
What is the miRBase database
Serachable database of publishe miRNA sequence each enetery represent a predicted hairpin portion of the miRNA mir and the information on the location and sequence of the mature miRNA miR
what does the first part represent of hsa-mir-123-5p
Homo sapiens numbering is when they were disocvered extension are either from the 3’ or the 5’ arm
Can a single miRNA recogninze mutiple targe genes
YES
What is the most critcal for target mRNA
Seed sequence region which is the first 2-8 nucleotides starting at the 5’end and counting to the 3’end
What is a 6mer
A perefect WC match between miRNA see and mRNA for six nucleotides
What is 7mer-m8
a perfect WC match from nucleotides2-8 of the miRNA seed
What is 7mer-A1
A perfect WC match from nucelotides 2-7 in addition to an A across from the miRNA nucleotide 1
What is a 8mer
a perfect WC match from nucleotides 2-8 of the miRNA with an addition to an A across from the miRNA nucleotide 1
What is the difference between perfect complemntarity and imperfect
Imperfect leads to inhibition of protien syntheis and perfect is degradation of the mRNA
What do miRNA exhibit in stress conditions
Phenotypic crisis
In response to stress what do cells do
Choose to restore or reporgram their gene expression patterns change in the expression of miRNA can affect the presence of different protiens
How do cells modulate miRNA upon stress
Change in the level of miRNA
Change in mRNA targets
Change in the mode of action of miRNA protien complex
Change in the activity of miRNA protien complex
What does the heat map show
Tha hypoxia changes the expression on many miRNA in HT29 cells in a time depende maner
What happens under normal conditions
It is repressed by miRNA A and B and has basal level of expression
What happens upon stress
Expression of mRNA target decrease in the level of miRNA C increase
What could also happen under stress conditions
mRNA increases if the level of miRNA B decrease
What is there a realtionship between
miRNA load and target mRNA expression
What is target mimicry
Individual miRNA can interact with different target mRNAs which are called mimics of mRNA of your intrest. mRNA increases if the expression of mRNA targets increase upon stress because the targets compete for the same binding of miRNA causing relief in the repression of mRNA targets
What is creation/deletion of miRNA binding sites
Upon stress cells could express different isoforms of the mRNA target where miRNA binding sitres could be created or delted
What happens if miRNA sites are created
Expresion of the isoform will be decrease
What if the miRNA sites are deleted
The expression of the isoform will be stabilized
