Regulation by the RNA Polymerase II CTD

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Regulation by the RNA Polymerase II CTD
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Regulation by the RNA Polymerase II CTD
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Regulation by the RNA Polymerase II CTD
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Alternative Splicing

• Transcripts of many eukaryotic genes are subject
  to alternative splicing
• This splicing can have profound effects on the
  protein products of a gene
• Can make a difference between
• Secreted or membrane-bound protein
• Activity and inactivity

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Alternative Splicing
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Splicing controls sex determination
SXL and TRA are SR RNA-binding proteins (ser arg
rich) DSX is a class II transcription factor
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Types of Alternative Splicing

• Alternative promoters
• Ignore or not an intron or an exon
• Alternative 5-splice sites can lead to inclusion
  or deletion of part of an exon
• Alternative 3-splice sites can lead to inclusion
  or deletion of part of an exon
• Polyadenylation causes cleavage of pre-mRNA and
  loss of downstream exons

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Regulation of Splicing

• Exons can contain signals recognized by SR
  proteins
• Exonic splicing enhancers (ESEs) stimulate
  splicing

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Regulation of Splicing

• Exons can contain signals recognized by SR
  proteins
• Exonic splicing silencers (ESSs) inhibit splicing

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Regulation of Splicing

• Introns can contain signals
• Intronic splicing enhancers (ISEs) stimulate
  splicing
• Intronic splicing silencers (ISSs) inhibit
  splicing

ISS
ISS
ISS
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Reporter Construct Detects ESS Activity
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Capping
early in transcription, before chain is 30 nt long
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Polyadenylation

• Factors assemble on the pre-mRNA guided by motifs
• Cleavage occurs
• Polymerase initiates poly(A) synthesis
• PAB II allows rapid extension of the oligo(A) to
  full-length

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PolyA and cap functions

• Protect mRNAs from degradation
• Enhance translatability of mRNAs
• Transport of mRNAs out of nucleus
• Efficiency of splicing mRNAs

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PolyA and cap functions