Positioning and functional structure of repliction time zones at the cystic fibrosis gene locus

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During the first two funding periods we investigated the dynamics of DNA replication. We could show, that large-scale movements are not involved in DNA replication 1,2. Therefore, we concentrated on the analysis of local replication dynamics. In results show that, in contrast to favored models 3-6, DNA as well as functional complexes of replication proteins display local dynamics. The protein complexes display local re-localizations, which are not due to movements of whole complexes, but due to local processes of assembly and disassembly of replication proteins. While the DNA poised to replicate can be translocated into these complexes, nascent DNA is extruded in an aggregated form into adjacent regions. Furthermore, the results showed that 93% of DNA aggregates, which replicated at a defined time point during S-phase, stably maintained their replication timing. These results strongly support the hypothesis, that chromosomes are organized into stable DNA aggregates (subchromosomal foci), which display a defined replication timing during S-phase 7-13. In order to further proof this hypothesis we will investigate the distinct replication time zones at the cystic fibrosis gene locus 14 during the next funding period. We will analyze, whether these distinct time zones are organized into stable subchromosomal foci displaying a defined regulation with regard to replication, transcription, and nuclear positioning.