Title

Identification and analysis of development-specific genes in {\it Euplotes crassus\/}

Date of Completion

January 1997

Keywords

Biology, Molecular|Biology, Microbiology

Degree

Ph.D.

Abstract

The protozoan ciliate Euplotes crassus contains two different nuclei within the same cell: the micronucleus and the macronucleus. During its sexual cycle the macronucleus develops from the micronucleus. This development is accompanied by vast DNA excision, rearrangement and elimination. In order to look for the potential protein machinery that is responsible for the above developmentally regulated processes, I created a screen that identifies genes that are exclusively expressed in a developing Euplotes cell. Through that screen I isolated and characterized two genes, conN1 and conF5. The putative protein encoded by conN1 showed significant similarity with transcription factor IISs from a variety of eukaryotic species. The putative conF5 protein did not show homology with any known protein.^ I also contributed in the isolation of three additional development specific genes, conZA7, conZA8 and conZB1. The conZB1 gene encodes histone H3 variant that specifically localizes to the developing macronucleus. The appearance of this protein coincided with changes in chromatin structure. Moreover, its peak levels of expression coincides with chromosome fragmentation events and its disappearance coincides with completion of DNA rearrangement. Therefore we speculate that conZB1 plays an important role in DNA rearrangement by altering the chromatin structure and making it accessible to the DNA rearrangement machinery. ^