Gene expression is regulated at many levels since changes in the expression pattern of certain genes might lead to the development of diseases such as cancer. Transcription is one of these regulation steps, orchestrated by transcription factors and RNA polymerases. Of these, RNA polymerase III (RNA Pol III) is responsible for transcribing small un-translated RNA molecules, such as tRNA. Transcription Factor (TF) IIIC (TFIIIC) binds to type 2 promoters (consisting of two conserved boxes, A and B), is thought to recruit TFIIIB and subsequently Pol III. Recently, TFIIIC has also been found bound to eight untranscribed B box related sequences, so-called Extra-TFIIIC (ETC) sites, in the absence of TFIIIB and Pol III. Binding of this transcription factor to ETC sites is thought to serve as an anchor point for other proteins, such as proteins involved in chromatin organization and gene silencing.The precise role of TFIIIC in extra transcriptional processes is not clear. The goal of this project is to address this issue by performing in vivo fluorescence cross correlation spectroscopy studies between TFIIIC, ETC sites and other key proteins involved in chromatin organization and transcription. With this method, and by using fluorescently tagged proteins, the interaction between TFIIIC and known and suspected interaction partners will be analysed. In addition, interaction of TFIIIC and ETC sites will be studied, as well as the biological significance of these interactions, by fluorescently tagging the ETC sites. These analyses will be done in a cell cycle dependent manner, to better understand in which cell cycle phase TFIIIC is most important.In summary, this project proposes a global study of the role of TFIIIC in extra-transcriptional processes. Together with biochemical data, it will contribute tor a better understanding of the function of TFIIIC in transcription regulation and of the mis-regulation of Pol III transcription in cancer development.