Intracisternal A-particle genes as movable elements in the mouse genome

Area of Science:

• Molecular Biology
• Genetics
• Retroviral Research

Background:

• Two functionally defective mouse kappa light chain gene variants were previously identified.
• These variants contained novel repetitive DNA insertions in their intervening sequences.

Purpose of the Study:

• To characterize the nature of the repetitive DNA insertions in mouse kappa light chain gene variants.
• To investigate the mechanism of insertion of these repetitive elements.

Main Methods:

• Heteroduplex analysis of cloned mouse kappa light chain genes.
• Restriction enzyme mapping to determine insertion boundaries.
• Nucleotide sequencing of intracisternal A-particle (IAP) long terminal repeat (LTR) sequences.

Main Results:

• The insertions were identified as intracisternal A-particle (IAP) genetic elements.
• Each insertion contained an IAP 5' long terminal repeat (LTR) and extended to an IAP internal BamHI site.
• Restriction mapping confirmed IAP LTR boundaries aligned with gene rearrangement sites; one IAP insertion contained a deletion absent in the other.
• Sequencing of IAP LTRs revealed features typical of integrated retroviral terminal repeat units, bracketed by direct repeats in adjacent cellular DNA.

Conclusions:

• Intracisternal A-particle (IAP) genetic elements can integrate into new locations within mouse cellular DNA.
• The findings suggest that proviral insertion is a potential mechanism for the movement of IAP elements.