endreplication

Endreplication is a term sometimes used to describe the set of processes that ensure replication of the ends of linear chromosomes, mitigating the end-replication problem. In standard literature, the term is not widely adopted; the mechanisms that perform this function are collectively referred to as telomere maintenance, including telomerase activity and alternative lengthening of telomeres (ALT).

Most DNA polymerases cannot fully replicate the 3' ends of linear DNA; without special mechanisms, chromosomes would shorten with every cell division. Endreplication involves adding telomeric repeats to the 3' end by telomerase, or in some cells, through recombination-based telomere elongation in ALT. Protective protein complexes such as shelterin in mammals bind telomeres to prevent erroneous DNA damage responses. In some contexts endreplication also encompasses end-processing steps and replication fork restart near telomeres.

Biological significance: Adequate endreplication preserves genomic integrity and cell viability; insufficient end replication leads to replicative senescence or apoptosis, while in most cancers, telomere maintenance is reactivated, enabling limitless replication.

Terminology: The label endreplication is not standard; textbooks more commonly use telomere maintenance or telomere replication. Some early or speculative writings may apply endreplication to the cumulative process of restoring chromosome ends.

See also: Telomere, Telomerase, Shelterin complex, ALT, End replication problem, DNA replication.