Lei Ding

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• Lei Ding
• J. Club 12-05-2008

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Non-coding RNA The hidden transcriptome

• Conventional ncRNAs rRNA, tRNA, miRNA, etc.
• Genome-wide expression analyses indicate big
• portion of transcripts in fission yeast are
  non- protein coding RNA.
• Previously thought functionally inert regions
  are found transcriptional active.
• Most large polyadenylated mRNAs have little
  coding potential

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• Chromatin
• Complex of DNA wrapping around histone proteins
  in nucleus.
• Highly dynamic structure

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Chromatin remodeling

• Highly condensed chromatin structure inhibits
  transcription by preventing the loading of
  transcription activator.
• Chromatin structure changes to open configuration
  coincides with transcription initiation.

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Background

• glucose-induced cAMP signalling inhibits
  gluconeogenesis by triggering the repression of
  the fructose-1,6-bisphosphatase (fbp1) gene.
• Fbp1 strongly induced by glucose starvation

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Long ncRNAs are transiently expressed upstream of
fbp1
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Transcription initiation sites of ncRNAs
c
a
d
b
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No protein produced by ncRNA
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Chromatin Imummoprecipitation (ChIP)
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RNAPII binding sites shift 5-3
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Stepwise Chromatin Remodeling coincides with
ncRNA transcription
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Passage of RNAPII is vital for chromatin
remodeling
Premature transcripts
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Passage of RNAPII is vital for chromatin
remodeling --continued
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Transcription factors collaborate with RNAPII
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UAS1 NaeI UAS2 EcoT221 TATA
fbp1
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Proposed model for fbp1 chromatin remodeling
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Atf1-Pcr1
RNAPII
Rst2
TUP
stablize
d
d
d
d
d
d
UAS1
UAS2
TATA
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Summary

• Stepwise chromatin remodeling induced by RNAPII
  transcription of long ncRNAs
• RNAPII collaborates with other transcription
  factors during this process.
• Transcription through the promoter region is
  required for transcriptional activation

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Discussion

• What is the role of ncRNAs in chromatin
  remodeling? It is vital in function or just
  by-products of RNAPII passage?
• What is the mechanism of initiation of ncRNAs?
  Are there any regulators?
• Why the ncRNAs are short lived?

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Thank you