RAG Recombinase as a Selective Pressure for Genome Evolution.

Area of Science:

• Genetics
• Molecular Biology
• Bioinformatics

Background:

• The RAG recombinase enzyme is crucial for V(D)J recombination in jawed vertebrates, essential for adaptive immunity.
• RAG targets, Recombination Signal Sequences (RSS), are degenerate, allowing interaction with non-canonical sites, posing a risk to genome integrity.
• Aberrant RAG activity can lead to DNA recombination and lymphoid malignancies.

Purpose of the Study:

• To develop a novel bioinformatics tool for mapping potential RAG target sites in jawed vertebrate genomes.
• To assess the tool's performance against existing methods and its applicability across diverse species.
• To investigate the evolutionary dynamics of RAG targets and their genomic context.

Main Methods:

• Development of the REcombination Classifier (REC) bioinformatics tool.
• Genome-wide scanning for potential RAG target sequences using REC.
• Comparative analysis of REC performance with existing RAG target prediction tools.
• Analysis of RAG target site distribution in relation to gene expression and epigenetic marks (H3K4me3).

Main Results:

• The REcombination Classifier (REC) demonstrates superior performance in identifying potential RAG targets compared to current tools.
• REC is effective for analyzing genomes beyond human and mouse.
• A reduced density of potential RAG targets was observed at transcription start sites of genes co-expressed with RAG and marked by H3K4me3.
• This finding correlates with the maintenance of functional RAG activity post-horizontal gene transfer.

Conclusions:

• The REC tool provides a robust method for studying RAG target site evolution and distribution across vertebrates.
• Genomic regions with specific epigenetic marks and gene co-expression patterns show reduced RAG target density, suggesting evolutionary adaptation.
• Understanding RAG target site distribution is key to comprehending genome evolution and preventing RAG-associated genomic instability.