Biological processes utilizing DNA as a template must contend with its packaging into chromatin, a complex array of nucleosomes and non-histone proteins which compact DNA into a loosely defined higher order structure. All processes like transcription and replication have to deal with chromatin, an essential additional layer of regulation. The importance of chromatin structure in transcription initiation is well established. A specific example is the murine rDNA gene which I studied intensively. TTF-I (Transcription Termination Factor I) activates the ribosomal gene in a chromatin context. Moreover, TTF-I also terminates the elongating RNA polymerase I and releases the rRNA. Nothing is known about transcription termination in chromatin. My initial experiments show a specific chromatin structure of the rDNA terminator region in vivo. The experiments showed as well, that multiple binding sites enable cooperative TTF-I binding to the rDNA terminator and allow specific transcription termination on chromatin in vitro. In this project I propose to study the influence of TTF-I on the rDNA terminator chromatin structure in vitro and implications for transcription termination.
