29 Flashcards
(33 cards)
two types of regulatory RNAs
tarns and cis acting RNAs
examples of antisense and/or trasn encoded regulation
miRNA and siRNAs
what are some examples of cis encoded regulation
iron response element in euk
riboswitches in bact
what are some ways RNAs can act as regulators by base pairing
block protein binding
change RNA structure
tether protein
ribonuclease III
recognizes dsRNA and cleaves it at a specific targeted location to transform it to mature RNA
how do that majority of sRNAs act
by base pairing with target mRNAs leading to changes in the translation or stability of the targets
example of RNA sponge
6S RNA
what does 6s rna do
binds to rna pol and blocks initiation when NTP are limiting
what are riboswitches
cis encoded RNA regulatory elements that fold into secondary strcutre that bind to small molecules and can regulate downstream events including transcription, translation, and splicing
what are some metabolites/ small molecules that function in riboswitches
atoms such as F, Mg
phosphorylated sugars
purines
vitamins B12
amino acids (s adenosyl methionine)
thyamine pyrophosphate
vitamin B1
what does TPP do
shuts down translation of the mRNA for the thiamine boisynthetic genes by binding to a riboswitch and sequestering the SD sequence
what did jorgensen do
isolated gene for purple colour and inserted and extra copy into petunias to try to make the purple colour deeper
jorgensen result
white sectors in the flowers caused by cells that make no purple colour enzyne- cosupression
balbombe process
viral gene inserted into tabacco plant and plant was exposed to virus but remained healthy and the conclusion is that the viral gene was silenved
balbombe result
in viral infected transgenic plants there appeared to be no mRNA from either the viral gene of from the newly introduced viral gene- post transcriptional gene silencing
what did baulvombe propose
that PTGS occurs when RNA base paris with target mRNA (antisense) and promotes destruction of the mRNA or inteference with its translation into protein but this wasnt actually found
what did they find that silenced plants made
large amount of small RNAs 25 nt in length
what did they find that silenced plants made
large amount of small RNAs 25 nt in length that were complementary to the target gene
what is the central theme behind colour in petunia flowers, immunity of plants to viruses, small RNA and turning elegans genes off selevtively
siRNA
tomato line experiment
5 lines containing ACO transgenes
ACO mRNA was amplified by RT-PCR and detected by hybridization with 35S lebelled ACO cDNA
low molecular weight RNA from the same five lines and a 30nt ACO antisens RNA were frcationated blotter and hybridized with ACO sense RNA
what did fire and mello notice
both sense and antisense RNA blocked expression in c elegans and that dsRNA worked better than ssRNA
unc-22 experiment
wild type- sinsusoidal and dec expression of unc-22 leads to twitching
fire and mello experiment
nejcted elegans with ssRNA targeted against unc-22 and wild type elegans with dsRNA as control expecting anti sense RNA to inhibit unc-22 expression and cuase twitching
