Chromosome dynamics in the yeast interphase nucleus

Little is known about the dynamics of chromosomes in interphase nuclei. By tagging four chromosomal regions with a green fluorescent protein fusion to lac repressor, we monitored the movement and subnuclear position of specif ic sites in the yeast genome, sampling at short time intervals. We found th at early and late origins of replication are highly mobile in G(1) phase, f requently moving at or faster than 0.5 micrometers/10 seconds, in an energy -dependent fashion. The rapid diffusive movement of chromatin detected in G (1) becomes constrained in S phase through a mechanism dependent on active DNA replication. In contrast, telomeres and centromeres provide replication -independent constraint on chromatin movement in both G(1) and S phases.