CSB349H1 Lecture Notes - Lecture 5: Small Nuclear Rna, Transcription Preinitiation Complex, Tata Box
14 May 2018
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Lecture 5(a): Transcription III
Pre-Initiation Complex (PIC):
• Formation of the PIC is the ‘rate limiting step’ in transcriptional regulation
o Mechanism controlling the assembly of the RNAPII transcription PIC essentially
control the rate of transcription of protein-coding regions
o PIC assembly is sequential – determined by DNase I Footprinting, EMSA and ChIP
• General (or basic) transcription factors are necessary (can be sufficient) for accurate
transcription initiation
o TFIIA, TFIIB, TFIID, TFIIE, TFIIF, TFIIH, other components of RNAPII
§ Multi-subunit mediator complex
o General TF work with RNAPII – vary completely with sequence specific TF
§ Sequence specific TF => regulating transcription of specific genes
§ General TF => required for gene expression anytime, any tissue, any gene
• General TF assemble on the core promotor in an ordered fashion to form the PIC
o PIC will direct RNAPII to the transcription start site (TSS)
• General TF also help melt the DNA duplex
o Allowing the template strand to enter the active site of RNAPII
• RNAPII:
o Transcribes protein-coding genes, small nuclear RNA (snRNA), microRNA, miRNA
• TFIID:
o Functions:
§ Forming a platform for TFIIB binding
§ Recognition of the TATA box, & initiator element
• TBP component
RNAP Function:
• RNAP functions to open up the double stranded helix of DNA and generate a
complementary RNA strand
Document Summary
Multi-subunit mediator complex: general tf work with rnapii vary completely with sequence specific tf. Sequence specific tf => regulating transcription of specific genes. Recognition of the tata box, & initiator element: tbp component. Rnap function: rnap functions to open up the double stranded helix of dna and generate a complementary rna strand. Pic assembly: assembly is sequential forms bit by bit , tfiid will bind to the dna, tfiid is the only one that is sequence specific, tfiid can recognize three promotor elements: In this case, tf11d will bind the tata box via tbp; cause an intense dna bend: tfiib & rnapii/tfiif, tfiib will bind onto tfiid. Tfiid forms a platform for tfiib: tfiif/rnapii is recruited and positioned over top of the tss. Tfiia (not shown) is also recruited: required for stability of tfiid and. Tfiib components in vivo: tfiie & tfiih: Tbp and other tfiid subunits will remain bound to the dna to allow very quick re-initiation.
