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Genome-wide Surveillance of Transcription Errors in Eukaryotic Organisms
09:30

Genome-wide Surveillance of Transcription Errors in Eukaryotic Organisms

Published on: September 13, 2018

Transcriptional bypass of bulky DNA lesions causes new mutant RNA transcripts in human cells

Cheryl Marietta1, Philip J Brooks

  • 1Section on Molecular Neurobiology, Laboratory of Neurogenetics, National Institute on Alcohol Abuse and Alcoholism, 5625 Fishers Lane, Room 3S-32, MSC 9412, Bethesda, Maryland 20892, USA.

EMBO Reports
|March 17, 2007
PubMed

Insights

Human RNA polymerase II (Pol II) bypasses DNA lesions, creating mutant transcripts. This process, known as transcriptional mutagenesis, can lead to deletions and misincorporations, influenced by DNA repair proteins like Cockayne syndrome B.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • DNA damage can impede transcription by RNA polymerase II (Pol II).
  • Specific DNA lesions, such as 8,5'-cyclo-2'-deoxyadenosine (cyclo-dA) and cyclobutane pyrimidine dimers (CPDs), are substrates for nucleotide excision repair (NER).
  • The consequences of Pol II encountering and bypassing these lesions in vivo are not fully understood.

Purpose of the Study:

  • To characterize the types of mutant transcripts generated by human Pol II bypassing cyclo-dA and CPD lesions in vivo.
  • To investigate the role of the Cockayne syndrome B (CSB) protein in the fidelity of transcription past DNA lesions.

Main Methods:

  • In vivo characterization of mutant transcripts produced by human Pol II.
  • Analysis of transcript sequences following bypass of cyclo-dA and CPD DNA lesions.
  • Comparison of transcript formation in wild-type and mutant human cell lines (e.g., CSB-deficient).

Main Results:

  • Bypass of cyclo-dA lesions by Pol II resulted in two types of mutant transcripts: those with base misincorporations (uridine opposite lesion, adenosine misincorporation downstream) and those with nucleotide deletions (7, 13, or 21 nt).
  • The frequency of deletion transcripts from cyclo-dA lesions was affected by the presence of functional Cockayne syndrome B protein, suggesting its role in modulating transcriptional mutagenesis.
  • Rare transcripts with 12 nt deletions were also observed when Pol II bypassed CPD lesions.

Conclusions:

  • Human RNA polymerase II can actively bypass helix-distorting DNA lesions in living cells.
  • Bypass of DNA lesions by Pol II leads to transcriptional mutagenesis, generating altered RNA transcripts.
  • The efficiency and type of mutations may be influenced by DNA repair proteins, highlighting the interplay between DNA repair and transcription.

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