Juan Mendez
In each mitotic cell cycle, the entire human genome is faithfully duplicated during a period of 6-8 hours that constitutes the S-phase. DNA replication initiates from multiple origins on the chromosome at different times, following a temporal program that is conserved from one cell cycle to the next. This temporally ordered process correlates with parameters related to gene activity, chromatin structure and nuclear position.

The activity of origins of replication is controlled by "initiator" proteins such as ORC, CDC6 and CDT1 and MCM2-7, which associate with the DNA prior to S-phase. At the G1-S transition, the activation of cyclin-dependent kinases (CDKs) and the Dbf4-Cdc7 kinase promotes the recruitment of additional proteins, such as Cdc45 and the GINS complex, which associate with MCM in a large complex (CMG) that likely constitutes the core of the replicative DNA helicase. The activation of certain oncogenes (e.g. Cyclin E) impairs the correct assembly of the DNA helicase machinery, affecting DNA replication and increasing genomic instability.

We study the molecular mechanisms of DNA replication in human cells, focusing on the following topics:

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Figure 1: Temporal programme of DNA replication across chromosome 11 in three different human cell lines. Peaks and valleys indicate areas of early or late DNA replication, respectively. Magenta, BJ-hTert-p53KD (immortalized primary fibroblasts); blue, U2OS (osteosarcoma cell line); yellow, Z138 (mantle cell lymphoma cell line).