In most eukaryotes, their chromosome ends are composed of a single stranded overhang that contains GT-rich repeats and are bound by telomerase ribonucleoproteins (RNPs).This entry represents a group of telomere binding proteins, including the protection of telomeres protein 1 (POT1) from humans/fission yeast/plants, the telomere end binding proteins (TEBP) alpha from the hypotrichous ciliate Oxytricha nova and Cdc13 from Saccharomyces cerevisiae. They are ribonucleoproteins (RNPs) that play an important role in telomere maintenance, but the precise roles played in end protection and telomere length regulation seem to vary considerably between organisms [, ]. In fission yeast, POT1 prevents access of telomerase to the 3'-end and protects against exonucleolytic degradation []. However, in humans, POT1 might function predominantly in telomere length regulation rather than in the protection of telomeres []. In Arabidopsis, there are several POT-like proteins, including POT1a, POT1b and POT1c []. POT1a and POT1b are components of telomerase rather than telomere capping components []. In Saccharomyces cerevisiae an OB-fold containing protein called Cdc13 plays a similar role as POT1, such as single-stranded G-rich telomeric DNA binding and telomere maintenance [, ].