Long terminal repeat-like elements flank a human immunoglobulin epsilon pseudogene that lacks introns

Area of Science:

• Genetics
• Molecular Biology
• Immunology

Background:

• The human genome contains at least three immunoglobulin epsilon genes (C epsilon 1, C epsilon 2, and C epsilon 3).
• Understanding the structure and evolution of these genes is crucial for insights into immune system function and genetic diversity.

Purpose of the Study:

• To compare the nucleotide sequences of the expressed C epsilon 1 gene and the C epsilon 3 pseudogene.
• To elucidate the structural characteristics and potential evolutionary origins of the C epsilon 3 processed gene.

Main Methods:

• Nucleotide sequence comparison between the C epsilon 1 gene and the C epsilon 3 pseudogene.
• Analysis of gene structure, including intervening sequences, flanking regions, and open reading frames.
• Identification and characterization of Long Terminal Repeat (LTR)-like sequences.

Main Results:

• The C epsilon 3 gene is a processed gene, lacking intervening sequences and possessing a unique A-rich sequence near the poly(A) signal.
• It exhibits homology to five distinct DNA segments of the C epsilon 1 gene (one 5'-flanking region segment and four exons).
• LTR-like sequences with TATAAA and AATAAA motifs and terminal inverted repeats are present in flanking regions, though not direct repeats. The 3' LTR-like sequence is repetitive in the genome but not homologous to Alu DNA.
• A novel open reading frame in C epsilon 3 potentially codes for a 292-amino acid protein.

Conclusions:

• The C epsilon 3 gene represents a processed gene with a unique structure, distinct from typical transposable elements.
• The flanking LTR-like sequences suggest potential mechanisms for its integration and evolution within the human genome.
• The identified open reading frame indicates the potential for a novel protein product derived from this processed gene.