Related Experiment Videos
Reading-frame restoration with an apolipoprotein B gene frameshift mutation
M F Linton1, V Pierotti, S G Young
1Gladstone Institute of Cardiovascular Disease, University of California, San Francisco 94141-9100.
Summary
A hypobetalipoproteinemia-causing mutant apolipoprotein B (apoB) allele unexpectedly produces full-length apoB. This occurs due to an adenine insertion during transcription, restoring the apoB reading frame.
Area of Science:
- Genetics
- Molecular Biology
- Biochemistry
Background:
- Hypobetalipoproteinemia is a genetic disorder linked to apolipoprotein B (apoB) mutations.
- A specific mutant apoB allele with a cytosine deletion in exon 26 was identified.
Purpose of the Study:
- To investigate the mechanism by which a mutant apoB allele, despite a frameshift mutation, produces a full-length apoB protein.
- To elucidate the role of adenine insertion in restoring the apoB reading frame.
Main Methods:
- Analysis of a mutant human apolipoprotein B (apoB) allele associated with hypobetalipoproteinemia.
- Minigene expression studies in cultured cells.
- Examination of cDNA from transfected cells to analyze mRNA splicing and apoB gene transcription.
Main Results:
- The mutant apoB allele, causing a frameshift, unexpectedly yielded a full-length apoB protein in addition to a truncated form.
- Analysis revealed that 11% of cDNA clones contained an extra adenine within a run of eight adenines, creating nine consecutive adenines.
- This adenine insertion is predicted to restore the correct apoB reading frame.
Conclusions:
- The mutant apoB allele can produce a full-length apoB protein through a mechanism involving adenine insertion during gene transcription.
- This insertion event corrects the frameshift mutation, allowing for the synthesis of functional apoB protein.
- Understanding this mechanism provides insights into apoB gene regulation and hypobetalipoproteinemia pathogenesis.