Transcription CSF 2

Central Dogma of Genetics

The flow of genetic information: DNA → RNA → Protein

Transcription

The process of copying a DNA sequence into RNA, occurs in the nucleus in eukaryotes

RNA Polymerase II

The enzyme that transcribes mRNA and most lncRNAs; most accurate and heavily regulated polymerase

RNA Polymerase I

The enzyme that transcribes large rRNAs (except 5S); located in the nucleolus; fastest polymerase

RNA Polymerase III

The enzyme that transcribes tRNAs, 5S rRNA, and other small non-coding RNAs

Promoter

DNA sequence upstream of a gene where transcription factors and RNA polymerase bind to initiate transcription

TATA Box

A conserved DNA sequence (TATAAA) in the promoter region that serves as a binding site for TFIID

Preinitiation Complex (PIC)

The complete assembly of transcription factors and RNA polymerase II at the promoter before transcription begins

TFIID

The first transcription factor to bind; recognizes TATA box via TBP subunit

TBP (TATA-Binding Protein)

Subunit of TFIID that binds to the TATA box and kinks the DNA

TFIIB

Transcription factor that recruits RNA polymerase II and helps determine the start site

TFIIH

The last transcription factor to bind; has helicase activity to unwind DNA and kinase activity to phosphorylate CTD

Promoter Melting

The unwinding of DNA double helix by TFIIH to form the transcription bubble

CTD (C-Terminal Domain)

The tail of RNA polymerase II that recruits processing enzymes when phosphorylated

Elongation

Phase of transcription where RNA polymerase synthesizes RNA while moving along the DNA template

Processivity

The ability of an enzyme (like RNA polymerase) to continue adding nucleotides without falling off

Transcription Bubble

The region of unwound DNA where transcription occurs

Template Strand (Antisense)

The DNA strand that is read by RNA polymerase (3'→5') to make complementary RNA

Coding Strand (Sense)

The DNA strand with the same sequence as the RNA (except T instead of U)

Negative Elongation Factors

Proteins that cause RNA polymerase II to pause shortly after initiation

P-TEFb (Positive TF)

Kinase that phosphorylates RNA polymerase II to promote elongation and overcome pausing

Termination

The process of ending transcription and releasing the RNA product

5' Capping

Addition of a modified guanine nucleotide to the 5' end of RNA; protects and marks mRNA

3' Polyadenylation

Addition of a poly-A tail to the 3' end after cleavage; protects RNA and aids export

AAUAAA

The conserved signal sequence for cleavage and polyadenylation

Splicing

The process of removing introns and joining exons from pre-mRNA

Spliceosome

The complex of snRNAs and proteins that catalyzes splicing

Intron

Non-coding sequence that is removed during splicing

Exon

Coding sequence that remains in the mature mRNA

Alternative Splicing

The process where different combinations of exons are joined to produce multiple protein isoforms

Isoforms

Different versions of a protein produced from the same gene via alternative splicing

hnRNA/pre-mRNA

The initial RNA transcript before processing occurs