title: Developmentally programmed gene elimination in Euplotes crassus facilitates a switch in the telomerase catalytic subunit.
abstract: The primary function of telomerase is to maintain preexisting telomere tracts. In the ciliate Euplotes crassus, however, telomerase RNP structure and substrate recognition are altered during macronuclear development to facilitate de novo telomere addition. We found that E. crassus harbors three TERT genes encoding the telomerase catalytic subunit that not only vary in their nucleotide and predicted protein sequences, but also in their expression profiles. Expression of EcTERT-1 and -3 correlates with the requirement for telomere maintenance, while that of EcTERT-2 correlates with de novo telomere synthesis. All three genes appear to require ribosomal frameshifting for expression of catalytically active protein. The transcriptionally active form of EcTERT-2 exists only transiently in mated cells and is absent from the vegetative macronucleus. Thus, telomerase expression in Euplotes is controlled by unique regulatory mechanisms that culminate in a developmental switch to a different catalytic subunit with properties suited to de novo telomere addition.
authors.affiliation: Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843, USA.
authors.forename: Zemfira
authors.initials: Z
authors.lastname: Karamysheva
authors.forename: Libin
authors.initials: L
authors.lastname: Wang
authors.forename: Timothy
authors.initials: T
authors.lastname: Shrode
authors.forename: Janna
authors.initials: J
authors.lastname: Bednenko
authors.forename: Leigh Anne
authors.initials: LA
authors.lastname: Hurley
authors.forename: Dorothy E
authors.initials: DE
authors.lastname: Shippen
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence / Q000235:genetics; D020134:Catalytic Domain / Q000235:genetics; D002455:Cell Division / Q000235:genetics*; D002874:Chromosome Mapping; D016812:Euplotes / Q000201:enzymology* / Q000235:genetics*; D016368:Frameshift Mutation / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D021122:Protein Subunits / Q000096:biosynthesis / Q000235:genetics*; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism; D019098:Telomerase / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D021122:Protein Subunits; D019098:Telomerase