Killin, p53-regulated DNA replication inhibitor (KLLN)

Killin (KLLN, p53-regulated DNA replication inhibitor) is a nuclear DNA-binding protein induced by the tumor suppressor p53, tightly involved in the regulation of the S phase checkpoint of the cell cycle. Upon activation (especially in response to genotoxic stress), KLLN binds DNA with high affinity—preferentially to single-stranded regions—to inhibit DNA synthesis, induce S phase arrest, and trigger apoptosis. KLLN appears essential for p53-mediated apoptosis but may also function through p53-independent mechanisms, contributing to maintenance of genome stability. Loss or silencing of KLLN, often through promoter hypermethylation, has been linked to increased malignancy risk in hereditary and sporadic cancers. KLLN is transcribed from a divergent promoter close to PTEN and may have coordinated expression with PTEN, another well-known tumor suppressor. No approved drugs currently target KLLN directly; its central involvement is as a mediator or effector in key cancer-associated pathways. Recognized as a candidate biomarker for certain cancer syndromes, especially with epigenetic inactivation. Sometimes referred to as a transcription factor due to its gene regulatory function, although its primary biochemical activity is DNA binding and inhibition of replication.

Other names

KillinKLLNCWS4KILLINkillinp53-regulated DNA replication inhibitor

Functions as a tumor suppressor by inhibiting DNA replication during S phase, leading to cell cycle arrest and apoptosis. For drugs affecting pathways involving KLLN, mechanisms may include activation of p53 and induction of DNA damage response. Research indicates killin is regulated by p53 and can be involved in response to genotoxic agents like doxorubicin and 5-fluorouracil, but no drugs directly target KLLN at this time.