6th ESACP Congress, Heidelberg, April 7-11, 1999

A018
NUCLEAR ORGANIZATION
van Driel R

EC Slater Institut, BioCentrum Amsterdam, University of Amsterdam, Amsterdam, Netherlands

The interphase nucleus is the most prominent organelle in the eukaryotic cell. It harbors the genetic information and all machineries involved in handling it, including the systems for gene silencing and activation, transcription, RNA processing and transport, and DNA replication and repair. Although many of these processes are understood quite well at the molecular level, the nuclear context in which they function is still largely unexplored. Although no direct proof is available yet, it is very likely that nuclear structure is highly significant for control of genomic activity. In this lecture I will discuss emerging principles of nuclear organization. A prominent aspect of nuclear organization is its compartmentalization. The classical compartment is the nucleolus, which is dedicated to transcription of rRNA genes and the assembly of ribosomes. Recent evidence shows that many more compartments exist that seem to serve specific classes of genes. Chromosome territories constitute another type of nuclear compartment. Each territory is occupied by one chromosome only and does not seem to be intruded by other chromosomes. The relationship between chromosome territories and the spatial distribution of transcription sites will be discussed.