Hi-C Calibration by Chemically Induced Chromosomal Interactions.

Area of Science:

• Genomics
• Molecular Biology
• Biophysics

Background:

• Hi-C is a powerful tool for studying genome organization and 3D chromatin structure.
• Assessing the quantitative properties of Hi-C, such as sensitivity and bias, is challenging due to dynamic cellular processes.
• In vivo validation of Hi-C's quantitative accuracy is difficult.

Purpose of the Study:

• To quantitatively assess the sensitivity, bias, and linearity of the Hi-C assay.
• To establish a robust framework for calibrating Hi-C data.
• To investigate the role of static intra-chromosomal loops in genome organization.

Main Methods:

• Utilized the Chemically Induced Chromosomal Interaction (CICI) method to create stable, engineered chromosomal interactions in G1-phase budding yeast.
• Performed Hi-C analysis on cell populations with engineered interactions across a range of contact frequencies.
• Analyzed Hi-C data to determine assay sensitivity, bias, and signal linearity.

Main Results:

• Static intra-chromosomal loops do not form Topologically Associated Domains (TADs) but induce local 3D proximity (<50kb).
• Hi-C can detect interactions present in 5-10% of cells at moderate sequencing depths.
• The Hi-C assay exhibits no bias between intra- and inter-chromosomal interactions and shows a linear relationship between signal intensity and contact frequency.

Conclusions:

• The CICI method provides a reliable system for evaluating Hi-C's quantitative performance.
• Hi-C is a sensitive and unbiased method for measuring genome-wide interactions.
• Findings offer a framework for calibrating Hi-C data and interpreting genome organization studies.