Stains & molecular markers

Topic Completed: 1 May 2016

Minor changes: 8 September 2020

Copyright: 2002-2021,, Inc.

PubMed Search: Ku80

Page views in 2020: 80
Page views in 2021 to date: 13
Cite this page: Thakur S, Enwere E. Ku80. website. Accessed January 16th, 2021.
Definition / general
  • 80 kDa subunit of the Ku complex
  • Functions with its heterodimeric partner Ku70 and the DNA ligase IV - XRCC4 complex in the repair of DNA double strand breaks by nonhomologous end joining (NHEJ)
  • Plays a critical role in the generation of novel antibodies and T cell receptors, through the process of V(D)J recombination
Essential features
  • Abundant, ubiquitously expressed nuclear protein that can bind to and stabilize the ends of free double stranded DNA
  • Ku70 / Ku80 heterodimer has ATP dependent DNA helicase activity and functions as the DNA binding component of DNA dependent protein kinase (DNA - PK) (Science 1998;280:741, Biochemistry 1994;33:8548, Mol Cell Biol 1990;10:6472)
  • Combined activities of Ku70 / Ku80 and DNA - PK are essential for DNA double strand break repair, telomere maintenance and many associated cellular functions
  • Also referred to as:
    • 86 kDa subunit of Ku antigen
    • ATP dependent DNA helicase II subunit 2
    • CTC box binding factor 85 kDa subunit
    • CTC85 or CTCBF
    • DNA repair protein XRCC5
    • FLJ39089
    • G22P2
    • KARP-1 or KARP1
    • Ku autoantigen 80kDa
    • Ku86, Ku86 autoantigen related protein 1 or Lupus Ku autoantigen protein p86
    • KUB2
    • NFIV or Nuclear factor IV
    • Thyroid lupus autoantigen (TLAA)
    • Xray repair complementing defective repair in Chinese hamster cells 5 (double strand break rejoining)
    • Xray repair cross complementing protein 5 (XRCC5)
  • Involved in various cellular processes including:
    • DNA duplex unwinding
    • DNA recombination
    • DNA double strand break repair
    • Double strand break repair via NHEJ
    • Innate immune response
    • Negative regulation of transcription, positive regulation of neurogenesis
    • Regulation of smooth muscle cell proliferation
    • Telomere maintenance
    • Transcription, DNA dependent viral reproduction (PhosphoSitePlus)

  • Expression of conditionally null allele in human somatic cells resulted in telomere loss and cell death (Proc Natl Acad Sci U S A 2009;106:12430)
  • Absence results in immune deficiency and absence of mature lymphocytes (Cell 1996;86:379)
  • Ku80 (- / -) mice prematurely exhibit signs of aging that include atrophic skin and hair follicles, osteopenia, premature growth plate closure, hepatocellular degeneration and shortened life span (Proc Natl Acad Sci U S A 1999;96:10770, Mol Cell Biol 2000;20:3772)
  • Ku80 (- / -) mice display a hypersensitivity to gamma irradiation, characterized by loss of hair pigmentation, severe injury to the gastrointestinal tract and enhanced mortality (Proc Natl Acad Sci U S A 1997;94:13588)
  • Loss of only a single allele in Ku (+ / -) heterozygous mice causes accelerated aging in skeletal muscle (EMBO Mol Med 2012;4:910)
  • Levels vary dramatically between species and strongly correlate with longevity of the species analyzed (Mech Ageing Dev 2009;130:784)
Clinical features
Microscopic (histologic) images

Images hosted on other servers:

Colon (normal)

Pancreas (normal)

IHC staining of Ku80 in
lung adenocarcinoma
and adjacent nontumor
lung tissues

Positive stains
  • Ku80 is ubiquitously expressed at high levels in most tissues
Negative stains
  • Liver and adipose tissue show medium to low levels of Ku80
Additional references
Back to top
Image 01 Image 02