Telomerase is a ribonucleoproteinreverse transcriptase that synthesises telomeric DNA. Telomerase RNAs differ greatly in sequence and structure between vertebrates, ciliates and yeasts, but they share a 5'pseudoknot structure close to the template sequence. Vertebrate telomerase RNAs have a 3' H/ACA snoRNA-like domain. This family also contains viral telomerase RNAs from the Gallid herpes viruses as described by Fragnet et al.[1]