Do non-genomically encoded fusion transcripts cause recurrent chromosomal translocations?

Area of Science:

• Molecular Biology
• Genetics
• Cancer Research

Background:

• Recent findings indicate normal cells produce fusion mRNAs.
• These fusion mRNAs originate from early-terminated transcripts (ETTs), not genomic rearrangements.
• ETTs arise from premature transcriptional termination within breakpoint cluster regions.

Purpose of the Study:

• To investigate the role of early-terminated transcripts (ETTs) in fusion mRNA generation.
• To explore the mechanisms of trans-splicing in normal and cancer-associated genes.
• To assess the potential of non-genomically encoded fusion transcripts (NGEFTs) in DNA repair.

Main Methods:

• Analysis of transcriptional termination and splicing patterns.
• Experimental investigation of four specific genes: ETV6, NUP98, RUNX1, and EWSR1.
• Comparative analysis of transplicing events across multiple cancer-associated genes.

Main Results:

• ETTs exhibit unsaturated splice donor sites, leading to cryptic exon splicing and trans-splicing (intra- and intergenic).
• Intergenic trans-splicing produces non-genomically encoded fusion transcripts (NGEFTs).
• Investigated genes (ETV6, NUP98, RUNX1, EWSR1) and previously studied genes (MLL, AF4, AF9, ENL, ELL) all show ETTs and trans-spliced mRNA species.

Conclusions:

• Trans-splicing via ETTs is a genuine mechanism for generating fusion transcripts from genes involved in translocations.
• NGEFTs may influence DNA repair processes by acting as guidance RNA.
• This mechanism provides a new perspective on gene expression regulation and potential oncogenic pathways.