RNA vs DNA stability

RNA less stable bc phospodiester bond is more susceptible to chem hydrolysis

modified bases

RNA bases

not AUGC

post-transcriptional modification

hairpins

intra-strand interactions of RNA

forms helices bc more stable than single strand

polycistronic vs monocistronic

in PRO, mRNA can encode more than one protein

in EU, each mRNA codes for 1 protein

unusually stable mRNAS (2)

mRNA in unfertilized egg (during arrest)

reticulocyte Hb mRNA has NO TURNOVER

methylated 5' cap

poly A tail

mRNA modifications that extend half-life

tRNA structure and functions

structure: Acceptor stem (binds aa), anticodon loop (binds mRNA)

fn:activate aa for protein synth (binds to acceptor stem), recognize mRNA codons

rRNA

abundance

most abundant cellular RNA (80%)

Svedburg units (S)

measure particles (ribosomal subunits)

snRNA (small nuclear RNA)

recognizes introns on mRNA participating in splicing

scRNA (small cytoplasmic RNA)

involved in selectoin fo proteins for export (signal recognition particle)

mtRNA (mitochondrial RNA)

r/t/mRNA transcribed from mitochondrial DNA

only ONE tRNA for each aa

RNP (ribonucleoprotein particles)

small RNA/protein molecules fn in RNA processing, splicing, transport, control blah blah blah

Ribozymes

RNA enzymes

RNAi (RNA interference)

control cell's phenotype by shutting down developmental genes or altering expression level

cellular differentiation

direction of RNA transcription/reading

like DNA, transcribed 5'-3', read 3'-5'

Pribnow box

TATAAT

promoter

not symmetrical (transcription can only go in 1 direction)

some promoters are stronger/weaker

RNA polymerases

catalyze RNA formation

build 5'-3'

DO NOT REQ PRIMER (unlike DNA polymerase)

NO PROOFREADING

PRO RNA polymerase

several subunits (together=holoenzyme, without sigma unit=core enzyme)

sigma subunit recognizes promoter

transcription bubble

EU RNA polymerases (3)

I: rRNA product, insensitive to alpha-amantin

II: mRNA product, v sensitive to amantin

III: tRNA product, sensitive to amantin

mitochondrial RNA polymerase sensitivity

sensitive to rifampicin, but not alpha-amantin

amanitin

mushroom poison, affects RNA polymerase II and III

rifampicin

antibiotic

mitochondrial RNA polymerase is sensitive to rifampicin

nucleolar organizer

regino of nucleolus, location of rRNA gene copies

primary transcript/pre-rRNA

each rRNA repeat (coding for diff subunits) is transcribed at the same time so equimolar amts of 3 subunits are created

product of transcription

primary transcript

mature RNA is formed after post-transcriptional processing

rRNA posttranscriptional modification

removal of nucleotides by ribonucleases (5' and 3' term seq + spacer seq)

tRNA posttranscriptional modification

ribozyme removes 5'end

-3'end + CCA

nuc base modification

mRNA posttranscriptional modification

+3' poly-A tail

+methylatoin of internal nucleotides

+methylated 5' cap

-introns (splicing) by snRNPs

alternative splicing

not all mRNAs from same gene are spliced in the same way

-->"family" of proteins