Most cancers prevent telomeres from shortening and thus stay alive by increasing the activity of an enzyme called telomerase, which can length telomeres. But some cancers uses a different method called ALT. Now researchers from the University of Pittsburgh Cancer Institute (UPCI) have identified that a DNA repair enzyme called Polη plays a role in the ALT pathway. Telomeres, which are protective DNA sequences at the end of chromosomes, plays important roles in many health conditions such as aging, cancer, and inflammation. Normally, telomeres become shorter every time a cell divides, and their length predicts how long the cell can live. When telomeres become too short, they send a signal to cell to stop dividing. But cancer cells can lengthen the telomere when it shortens, leading to tumor formation and spread. One of the mechanisms is that cancer cells elevate the activity of telomerase, an enzyme that lengthens telomeres. The increase in the activity off telomerase allows cancer cells to divide indefinitely. Furthermore, some cancers adopt another approach -- the alternative lengthening of telomeres (ALT) pathway -- to elongate telomeres. Recent studies have shown that cancers that have activated ALT pathway are aggressive and hard to treat. But the ALT pathway is not fully understood. Understanding its working mechanism will probably facilitate the development of drugs for cancer. In the new study, Dr Roderick O'Sullivan and colleagues from UPCI investigated the ALT pathway by using an advanced technique known as BioID. The researchers compared cancer cells in which either ALT or telomerase was activated, and finally discovered 139 proteins unique to ALT-activated cells. One of the proteins, called DNA polymerase η (Polη), is an enzyme that is involved in DNA repair. Polη was thought to be activated only in cells damaged by UV light. So the researchers were quite surprised to find it activated in cancer cells. The finding that Polη plays a role in the ALT pathway would extend the understanding of cancer development. CusAb has various proteins and antibodies such as Recombinant ECE1
