TELOMERASE RNA LOCALIZED IN THE REPLICATION BAND AND SPHERICAL SUBNUCLEAR ORGANELLES IN HYPOTRICHOUS CILIATES

The intranuclear distribution of telomere DNA-binding protein and telomerase RNA in hypotrichous ciliates was revealed by indirect fluorescent antibody staining and in situ hybridization. The Oxytricha telomere protein colocalized with DNA, both being dispersed throughout the macronucleus except for numerous spherical foci that contained neither DNA nor the protein. Surprisingly, the telomerase RNA was concentrated in these foci; therefore, much of telomerase does not colocalize with telomeres. These foci persist through the cell cycle. They may represent sites of assembly, transport or stockpiling of telomerase and other ribonucleoproteins. During S phase, the macronuclear DNA replication machinery is organized into a disc-shaped structure called the replication band, Telomerase RNA is enriched in the replication band as judged by fluorescence intensity. We conclude that the localization of a subfraction of telomerase is coordinated with semiconservative DNA replication.