This thesis describes the molecular dissection of the function of Cdc6 and the miR-148/152 family. We demonstrate that phosphorylation of the DNA replication initiation protein Cdc6 by CDK2/Cyclin... Show moreThis thesis describes the molecular dissection of the function of Cdc6 and the miR-148/152 family. We demonstrate that phosphorylation of the DNA replication initiation protein Cdc6 by CDK2/Cyclin E at serine 54 plays a key role in regulating its protein stability. In response to DNA damage, CDK2/Cyclin E activity will be inhibited, which results in reduced Cdc6 protein level. This regulatory mechanism might prevent initiation of DNA replication in the presence of DNA damage. Loss of p53 results in increased CDK2/cyclin E activity, and our data suggests that the increased stability of Cdc6 in p53 negative cells might be involved in the increased proliferative capacity of these cells. Next we studied several aspects of the miR-148/152 family. We revealed a novel mechanism of miRNA regulation, as we found that Dnmt3b is regulated by miR-148 through interaction with its protein coding region. We studied the function of this miRNA family in more detail in human T-cell development and in cell cycle progression of primary fibroblasts. Theses studies revealed a possible role of these miRNAs in regulation of proper S-phase progression and cell proliferation. Show less
