Predictable dynamic program of timing of DNA replication in human cells.

Area of Science:

• Genomics
• Molecular Biology
• Cell Biology

Background:

• Mammalian DNA replication organization remains largely unknown.
• Understanding replication timing is crucial for cell cycle regulation and genome stability.

Purpose of the Study:

• To create high-resolution dynamic maps of DNA replication timing in human cells.
• To investigate the relationship between replication timing and gene expression.
• To develop a method for predicting tissue-specific replication timing.

Main Methods:

• Utilized TimEX (Timing of Replication via EXpression) method employing Gaussian convolution of DNA copy-number variations.
• Applied high-density oligonucleotide tiling arrays and massively parallel sequencing for genome-wide analysis.
• Employed single-molecule analysis of replicated DNA (SMARD) to confirm replication fork progression.

Main Results:

• Generated high-resolution replication timing maps for human erythroid, mesenchymal, and embryonic stem (ES) cells.
• Demonstrated highly regulated and synchronous replication in untransformed human cells.
• Identified a strong inverse relationship between replication timing and proximity to expressed genes.
• Observed distinct replication patterns between ES and erythroid cells for approximately 20% of the genome.
• Found preferential localization of early replication origins near highly expressed genes and late origins far from genes.

Conclusions:

• Replication timing is a highly organized and cell-specific process in humans.
• Gene expression levels significantly influence replication origin firing and timing.
• The developed method can predict tissue-specific replication timing profiles using expression data.