TOP2A（topoisomerase (DNA) II alpha），癌症关联基因，基因ID：7153，这个基因编码一种DNA拓扑异构酶，这种酶在转录过程中控制和改变DNA的拓扑状态。这种核酶参与诸如染色体凝聚、染色单体分离以及DNA转录和复制过程中发生的扭转应力的减轻等过程。它催化双链DNA的两条链的瞬间断裂和重新结合，使双链彼此穿过，从而改变DNA的拓扑结构。这种酶有两种形式，可能是基因复制事件的产物。编码这种形式的基因α定位于17号染色体，β基因定位于3号染色体。编码这种酶的基因作为几种抗癌药物的靶点，并且这种基因的多种突变与耐药性的发展有关。这种酶活性的降低也可能在共济失调毛细血管扩张症中起作用。This gene encodes a DNA topoisomerase， an enzyme that controls and alters the topologic states of DNA during transcription. This nuclear enzyme is involved in processes such as chromosome condensation， chromatid separation， and the relief of torsional stress that occurs during DNA transcription and replication. It catalyzes the transient breaking and rejoining of two strands of duplex DNA which allows the strands to pass through one another， thus altering the topology of DNA. Two forms of this enzyme exist as likely products of a gene duplication event. The gene encoding this form， alpha， is localized to chromosome 17 and the beta gen。