Translocation Breakpoints Preferentially Occur in Euchromatin and Acrocentric Chromosomes

Area of Science:

• Genetics
• Cancer Biology
• Genomics

Background:

• Chromosomal translocations are key drivers in hematological and solid cancers.
• Factors like chromatin density, gene density, and CTCF/cohesin sites influence translocation breakpoint locations.
• These factors are often interdependent, complicating analysis.

Purpose of the Study:

• To identify primary predictors of non-random translocation breakpoint occurrence in cancer genomes.
• To investigate differences in translocation signatures between blood and solid tumors.
• To explore the spatial and selective forces shaping translocations during cancer development.

Main Methods:

• Analysis of 13,844 karyotypes from human blood cancers and 1563 from solid cancers.
• Multiple regression analysis to identify significant predictors of breakpoint location.
• Pairwise probabilistic co-occurrence modeling to assess translocation frequencies and selection.

Main Results:

• Open chromatin is the primary statistically significant predictor for translocation breakpoints.
• Blood and solid tumors exhibit distinct translocation signatures.
• Translocation breakpoints are more frequent in acrocentric chromosomes, suggesting nucleolar proximity.
• Underrepresented translocations with putative fusion genes indicate negative selection.

Conclusions:

• Chromatin accessibility is a major determinant of translocation generation in cancer.
• Translocations may frequently originate in the nucleoplasm, away from the nuclear envelope.
• Cancer evolution involves selection against certain translocation-induced gene fusions.