DNA ligase: it is an enzyme that catalyzes the joining of two strands of DNA, it forms a phosphodiester bond between them.
Topoisomerase II: it change DNA topology by generating transient DNA double strands breaks.
Telomerase: is resposible of restoring short bits of DNA (telomeres) by addition of guanine-rich repetitive sequences. This is necessary because when cell divides via mitosis, DNA is shortened and important information could be lost .