Worm Breeder's Gazette 13(2): 24 (February 1, 1994)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
Telomeres confer stability to the chromosome ends by protecting them from degradation and illegitimate recombination and might contribute to the spatial organization of the chromosomes in the nucleus. Furthermore, they affect the expression of telomeric proximal genes and might be involved in the mechanism of somatic cell aging (for review see Biessmann and Mason, 1992, Advances in Genetics 30, 185-249). The protecting telomeric extremities of the chromosomes are maintained by special enzymes, the telomerases, which add repeats of the telomeric sequence after each round of replication (for review see Blackburn, 1992, Ann. Rev. Biochem. 61, 113-129). Telomerases are ribonucleoproteins, acting as RNA dependent DNA polymerases, which contain their own RNA template as an integral part of the enzyme, unlike the conventional reverse transcriptases. The RNA component of telomerases from several Ciliates species has been identified and cloned, but all attempts to clone the gene(s) for the protein component(s) from any system have failed so far.
We assume that new telomere formation during the process of chromatin diminution in A. Iumbricoides requires a strong telomerase activity to resynthetize several kilobases of telomeric sequences in somatic cells (for review see Tobler et al., 1992, TIG 8, 427-432). In vitro extracts from eliminating developmental stages might thus be well suited for the isolation of the telomerase protein (or other factors) and for the cloning of the corresponding genes. Therefore, extracts from 4-8 cell stages were established and their quality was assessed by the ability to transcribe 5S rRNA genes (pol III) and SL RNA genes (pol II). Faithful in vitro extracts were tested for telomerase activity; our preliminary results revealed a possible nonprocessive and RNAse sensitive telomerase activity, capable of adding specific nucleotide sequences to the oligonucleotide primer (TTAGGC)(4). Currently, these data are being confirmed and extended. In a parallel approach, we will try to identify the C. elegans telomerase gene genetically.