Characterization of a histone deacetylase in Tetrahymena thermophila

摘要

Histone deacetylases (HDACs) have been implicated in several models for the assembly of heterochromatin. To investigate the role of HDACs in heterochromatin formation, we used the biological features of Tetrahymena as a model. Vegetative cells possess 2 nuclei: a large somatic, transcrip-tionally active macronucleus and a smaller germline, tran-scriptionally silent micronucleus. We have identified a novel putative class II HDAC in Tetrahymema (THD2) that is alternatively spliced. The transcript for the predominant form of Thd2 (Thd2a) encodes a protein with both an HDAC domain and an inositol polyphosphate kinase domain, which has been implicated in the regulation of ATP-dependent chromatin-remodeling complexes. Our preliminary studies demonstrate that Thd2a is highly enriched in the silent micronucleus during vegetative growth. An expression profile indicated that both forms of THD2 are not expressed during a brief stage in conjugation in which mi-cronuclei undergo transcription. Together, these results suggest an important role for THD2 in the maintenance of transcriptionally silent heterochromatin in the micronucleus.