Future Plans
Initiation of DNA replication will be further studied by characterizing the protein-protein interaction network at replication origins. We are particularly interested in analyzing the interactions between Cdc45p, RecQL4 and TopBP1 (in cooperation with Frank Hänel, HKI Jena), and their partners at the initiating, elongating as well as stalled or disturbed replication fork. We will concentrate on the biochemical, enzymatic and structural characterisation of these proteins and on the dynamics of their functional interactions. Therefore, it will be important to identify the post-translational modifications that regulate these proteins. Cell biological approaches such as replication in isolated nuclei will be used to study the replication function of these proteins.
The zebrafish has been proven a promising model to study the deficiency of Cdc45, TopBP1 and RecQL4 in vertebrates. We have been surprised by the complexity of the phenotypes that could not be predicted from cellular or biochemical studies. We will therefore continue our work on the role of initiation factors at the organismic level.
Our recent work points to cooperative functions of WRN and NDH II both during disturbed transcription and during disturbed DNA replication. Furthermore, Cdc45 may represent a general helicase cofactor that is able to coordinate DNA unwinding and rearrangements at the replication fork. We want to understand how cooperation of WRN, NDH II and Cdc45 contributes to the maintenance of genome stability. Biochemical and cell biological analysis will therefore be combined to define the functional interactions of these factors during DNA replication and transcription in detail.
Considering the pharmacological importance of cyclosporine A and its main cellular target cyclophilin 18, we would like to understand in which way long-term CsA treatment contributes to genomic instability. We will therefore look at the role of Cyp18 during the p53-dependent UV response and the repair capacity of the cell. We would also like to understand the cooperative and/or antagonistic effects of the two peptidyl-prolyl isomerases Cyp18 and Pin1 on p53. Finally, we will continue to study the differences between the naturally occurring p53 variant proline 72 and arginine 72 as biochemical modulators of the DNA damage response.
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