SCIE1106 Lecture Notes - Lecture 9: Sigma Factor, Helicase, Barcelona Metro Line 9
L9 Transcription
DNA -> mRNA, tRNA, rRNA
• Itergei spaes are’t trasried as they
have key features for other activities
• Only mRNA directs protein synthesis
• RNA polymerase binds to Promoter, and makes
complementary bases from template (that is
fro ’ to 5’) fro Prooter to Teriator
• RNA is writte fro 5’ to ’, sae as
coding/sense strand except mRNA has U
instead of T
• only 1 strand of RNA is copied
RNA synthesis (transcription) requirements
1. Mg2+
2. RNA polymerase (RNAP) – initiation,
elongation, termination
3. DNA template ( no primer required )
4. Four 5’ triphosphates that binds to 3’ of
template strands
a. 5’ ATP 5’GTP 5’CTP 5’UTP
RNA polymerase
• like DNA polymerase, forms phosphodiester
bonds between ribunucleosides ( to link them
all together) e.g A-phosphodiester bond- C-
p.bond-G
• use ATP for polymerization
• unlike DNA, RNA polymerase synthesis without
a primer
• rate than DNA polymerase
• unwindig of DNA heliase does’t eed
helicase / ATP – it pulls the template strand
away and starts building RNA molecules,
complementarily w/o the need of helicase/ATP
that pride apart dsDNA
RNA polymerase for E.coli / bacteria / prokaryotes
1. has 5 subunits (2 x a, b, b’ ad w) – aBB’w =
core enzyme
2. a mixes with core enzyme = holoenzyme, a is
responsible with promoter recognition (e.g -
35box -10box)
3. when initiation is achieved, “a” leaves
holoenzyme during elongation and core
enzyme continues elongation of RNA chain
there are multiple diff kinds of sigma factors in the cell -
diff sigma factors associate with diff RNA polymerase -
this guides different RNA polymerase to bind to other
networks - while others remain silent –
find more resources at oneclass.com
find more resources at oneclass.com
