## Description

This annotation shows smoothed replication timing for DNA synthesis as the time of 50% replication (TR50).

## Display Conventions and Configuration

This annotation follows the display conventions for composite tracks. The subtracks within this annotation may be configured in a variety of ways to highlight different aspects of the displayed data. The graphical configuration options are shown at the top of the track description page, followed by a list of subtracks. To display only selected subtracks, uncheck the boxes next to the tracks you wish to hide. For more information about the graphical configuration options, click the Graph configuration help link.

## Methods

The experimental strategy adopted to map this profile involved isolation of replication products from HeLa cells synchronized at the G1-S boundary by thymidine-aphidicolin double block. Cells released from the block were labeled with BrdU at every two-hour interval of the 10 hours of S-phase and DNA was isolated from them. The heavy-light (H/L) DNA representing the pool of DNA replicated during each two-hour labeling period was separated from the unlabeled DNA by double cesium chloride density gradient centrifugation. The purified H/L DNA was then hybridized to a high-density genome-tiling Affymetrix array comprised of all unique probes within the ENCODE regions.

The time of replication of 50% (TR50) of each microarray probe was calculated by accumulating the sum over the five time points and linearly interpolating the time when 50% was reached. Each probe was also classified as temporally specific or non-specific based on whether at least 50% of the accumulated signal appeared in a single time point or not.

The TR50 data for all specific probes were then lowess-smoothed within a 60 kb window to provide the profile displayed in the annotation.

## Verification

The replication experiments were completed for two biological sets in the HeLa adherent cell line.

## Credits

Data generation and analysis for this track were performed by the DNA replication group in the Dutta Lab at the University of Virginia: Neerja Karnani, Christopher Taylor, Hakkyun Kim, Louis Lim, Ankit Malhotra, Gabe Robins and Anindya Dutta.

Neerja Karnani and Christopher Taylor prepared the data for presentation in the UCSC Genome Browser.

## References

Jeon, Y., Bekiranov, S., Karnani, N., Kapranov, P., Ghosh, S., MacAlpine, D., Lee, C., Hwang, D.S., Gingeras, T.R. and Dutta, A. Temporal profile of replication of human chromosomes. Proc Natl Acad Sci U S A 102(18), 6419-24 (2005).