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A small upstream open reading frame causes inhibition of human major vault protein expression from a ubiquitous mRNA

K Holzmann1, I Ambrosch, L Elbling

  • 1Division of Cell Biology, Institute of Cancer Research, Vienna University, Austria.

FEBS Letters
|April 12, 2001
PubMed

Insights

Major vault protein (MVP) expression is regulated by alternative splicing. A long splice variant (L-MVP) inhibits MVP expression, impacting multidrug resistance (MDR) phenotypes in cancer cells.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • Overexpression of the major vault protein (MVP) is associated with multidrug resistance (MDR).
  • MVP plays a role in cellular resistance to various drugs.
  • Understanding MVP regulation is crucial for cancer therapy.

Purpose of the Study:

  • To investigate the role of MVP mRNA splice variants in regulating MVP expression.
  • To determine the impact of these variants on MDR phenotypes.
  • To explore alternative splicing as a mechanism for MVP regulation.

Main Methods:

  • Identification and characterization of MVP mRNA splice variants.
  • Analysis of the 5'-leader sequence, including upstream open reading frames (uORFs).
  • Comparison of splice variant ratios in normal and malignant tissues, and drug-sensitive vs. MDR cell lines.

Main Results:

  • A ubiquitously expressed long (L)-MVP splice variant was identified, differing in the 5'-leader from the short (S)-MVP isoform.
  • L-MVP mRNA contains a uORF that inhibits MVP expression both in vitro and in vivo.
  • The ratio of S-MVP to L-MVP mRNA varied between normal and malignant tissues and was altered in MDR cell sublines.

Conclusions:

  • Alternative splicing of MVP mRNA is a significant regulatory mechanism.
  • The L-MVP variant, through its uORF, acts as a negative regulator of MVP expression.
  • Altered S-MVP/L-MVP ratios may contribute to the development of multidrug resistance in cancer.

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