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Defective interplay of activators and repressors with TFIH in xeroderma pigmentosum

J Liu1, S Akoulitchev, A Weber

  • 1Gene Regulation Section, Laboratory of Pathology, National Cancer Institute, National Institute of Health, Bethesda, MD 20892, USA.

Cell
|March 10, 2001
PubMed

Insights

Mutations in TFIIH subunits xeroderma pigmentosum (XP) B and XPD disrupt transcription regulation of the c-myc gene. This subtle transcription defect, not just DNA repair issues, contributes to cancer risk in XP patients.

Area of Science:

  • Molecular Biology
  • Genetics
  • Cancer Research

Background:

  • Inherited mutations in TFIIH helicase subunits XPB and XPD cause overlapping DNA repair and transcription syndromes.
  • The high cancer risk in xeroderma pigmentosum (XP) patients is not fully explained by DNA repair defects alone.
  • Transcription defects in XP are subtle and challenging to evaluate.

Purpose of the Study:

  • To investigate the impact of XPB and XPD mutations on transcription regulation by FUSE Binding Protein (FBP) and FBP Interacting Repressor (FIR).
  • To elucidate the role of TFIIH in FBP-mediated transcription activation and FIR-mediated repression.
  • To understand the implications of impaired TFIIH function in c-myc expression and malignancy development.

Main Methods:

  • Investigated the interaction between TFIIH subunits (XPB, XPD) and transcription regulators FBP and FIR.
  • Assessed the effect of XPB and XPD mutations on FBP-dependent transcription activation and FIR-dependent repression.
  • Analyzed the regulation of c-myc gene expression in the context of TFIIH mutations.

Main Results:

  • XPB and XPD mutations were found to block transcription activation by FBP.
  • Mutations also impaired FIR-mediated repression of transcription.
  • TFIIH facilitates FBP-mediated transcription until promoter escape and FIR-mediated delay after initiation.
  • Impaired TFIIH regulation by FBP and FIR affects c-myc expression.

Conclusions:

  • TFIIH mutations affecting FBP and FIR regulation disrupt proper c-myc expression control.
  • These transcription dysregulations contribute to the high malignancy risk observed in XP patients.
  • Understanding these transcription defects is crucial for evaluating XP syndromes and cancer development.

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