[Telomer and telomeraze protective mechanism for chromosomes]

ABSTRACT

Telomer consists of two parts telos and mers. telos means end and mer means part. The unique functional properties of chromosome ends were first noticed in the 1930s by the fly geneticist Herman Muller. Telomeres are capping structures at the ends of eukaryotic chromosomes, which consist of repetitive DNA bound to an array of specialized proteins. In most eukaryotes, telomeres are formed by tandem arrays of short G/C-rich repeats. The telomeric G-rich strand is always oriented with its 3' end towards chromosome termini and forms short single-stranded protrusions called G-overhangs. The length of single-stranded protrusions range from 50 to 200 nucleotides and the current model predicts that G-overhangs are tucked into a duplex telomere forming so called t-loops. The function of telomeres is to prevent chromosome ends from being detected as damaged DNA. Both the length of telomere repeats and the integrity of the telomere-binding proteins are important for telomere protection. Telomere length is regulated by telomerase, by the telomere-binding proteins, as well as by activities that modify the state of the chromatin. This review discuss about function of the protection in the chromosome end in mammals, yeast, drosophila