The Paramecium germline genome provides a niche for intragenic parasitic DNA: evolutionary dynamics of internal eliminated sequences.

Insertions of parasitic DNA within coding sequences are usually deleterious and are generally counter-selected during evolution. Thanks to nuclear dimorphism, ciliates provide unique models to study the fate of such insertions. Their germline genome undergoes extensive rearrangements during development of a new somatic macronucleus from the germline micronucleus following sexual events.

Developmentally programmed DNA splicing in Paramecium reveals short-distance crosstalk between DNA cleavage sites.

Somatic genome assembly in the ciliate Paramecium involves the precise excision of thousands of short internal eliminated sequences (IESs) that are scattered throughout the germline genome and often interrupt open reading frames. Excision is initiated by double-strand breaks centered on the TA dinucleotides that are conserved at each IES boundary, but the factors that drive cleavage site recognition remain unknown. A degenerate consensus was identified previously at IES ends and genetic analyses confirmed the participation of their nucleotide sequence in efficient excision.

RNA-mediated programming of developmental genome rearrangements in Paramecium tetraurelia.

The germ line genome of ciliates is extensively rearranged during development of the somatic macronucleus. Numerous sequences are eliminated, while others are amplified to a high ploidy level. In the Paramecium aurelia group of species, transformation of the maternal macronucleus with transgenes at high copy numbers can induce the deletion of homologous genes in sexual progeny, when a new macronucleus develops from the wild-type germ line.

Isolation and expression of two genes encoding eukaryotic release factor 1 from Paramecium tetraurelia.

Paramecium tetraurelia, like some other ciliate species, uses an alternative nuclear genetic code where UAA and UAG are translated as glutamine and UGA is the only stop codon. It has been postulated that the use of stop codons as sense codons is dependent on the presence of specific tRNAs and on modification of eukaryotic release factor one (eRF1), a factor involved in stop codon recognition during translation termination. We describe here the isolation and characterisation of two genes, eRF1-a and eRF1 b, coding for eRF1 in P.

Resveratrol inhibits the growth and induces the apoptosis of both normal and leukemic hematopoietic cells.

It is often postulated that trans-3,4',5-trihydroxystilbene (resveratrol, RES) exhibits cell growth regulatory and chemopreventive activities. However, mechanisms by which this polyphenol inhibits tumor cell growth, and its therapeutic potential are poorly understood. Using various human leukemia cells, we have first defined the anti-tumoral doses of this compound.

Non-Mendelian inheritance and homology-dependent effects in ciliates.

Ciliates are single-celled eukaryotes that harbor two kinds of nuclei. The germline micronuclei function only to perpetuate the genome during sexual reproduction; the macronuclei are polyploid, somatic nuclei that differentiate from the micronuclear lineage at each sexual generation. Macronuclear development involves extensive and reproducible rearrangements of the genome, including chromosome fragmentation and precise excision of numerous internal sequence elements.