Transcription

• Overview of transcription• Process of transcription• Initiation • Elongation • Termination• Eukaryotic transcription

Overview of transcription

• Define transcription • Difference in RNA

and DNA • location in prokaryotic

and eukaryotic cells • What is a gene?

Process of transcription

• What is a gene? • Orientation of genes

Process of transcription

• sense strand (genetic code) • Anti-sense strand (template)

Initiation

• Promoters

• consensus sequence

• strength of the promoter

• -10 Pribnow Box

RNA Initiation

Initiation

• Role of RNA polymerase (open DNA helix) • sigma factor in initiation• Has proofreading ability

Elongation

• 5' to 3' growth of strand

• phosphodiester bonds • chain growth like in

DNA • only core enzyme of

RNA polymerase needed

• 30-50 nucleotides/sec

TerminationRho-factor

Termination: Rho independent

Eukaryotic transcription

• Location • Three RNA

polymerases • Goldberg-Hogness

box (TATA)• CAAT box • Processing of mRNA

in Eukaryotes

Eukaryotic transcriptionPromoter sites in Eukaryotes RNA polymerase

mRNA Processing

• 5' Cap • Poly A Tail; Poly A

polymerase • Exons and introns• Splicing of mRNA,

spliceosome• transport out of the

nucleus

5' Cap Poly A Tail; Poly A polymerase

Splicing of mRNA

• Autocatalytic RNAs: Self-Excision

• Group I introns(rRNA)

• Group II introns from pre-mRNA and pre-tRNA in mito/chloroplasts

• Guanosine cofactor

Splicing of mRNA• Spliceosome: snRNA’s

(100-200 nucleotides)• Removal introns in pre-

mRNA• snRNPs =

ribonucleoproteins• Rich in uridines• U1 complementary to the

5’ donor region in intron