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Gene Review

Irbp  -  Inverted repeat-binding protein

Drosophila melanogaster

Synonyms: ATP-dependent DNA helicase 2 subunit 1, ATP-dependent DNA helicase II subunit dp70, ATP-dependent helicase Irbp, CG5247, DmKu70, ...
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High impact information on Irbp

  • The mutant Dmblm phenotypes were partially rescued by an extra copy of the DNA repair gene Ku70, indicating that the two genes functionally interact in vivo [1].
  • Our findings provide the first demonstration that a mutation in the IRBP gene affects double-strand DNA break repair and suggest that DNA repair functions are conserved between Drosophila and mammals [2].
  • We have used RNA interference (RNAi) to knock down expression of DmBLM and one or both of the Drosophila Ku subunits, DmKu70 or DmKu80 [3].
  • We have established in yeast a connection between Ku activity and DNA double-strand-break damage repair, and a connection between Ku activity and commitment to DNA replication [4].
  • DNA double-strand-break sensitivity, DNA replication, and cell cycle arrest phenotypes of Ku-deficient Saccharomyces cerevisiae [4].

Biological context of Irbp

  • Cytogenetic mapping indicates that the IRBP gene maps to chromosomal position 86E on the right arm of the third chromosome [5].
  • Biochemical studies have identified a cellular non-P element-encoded DNA binding protein, termed the inverted repeat binding protein (IRBP), that specifically interacts with the outer half of the 31-bp terminal inverted repeats [5].
  • In descending order of affinity, YPF1 binds to: specific DNA sequences with a specific polarity and spacing relative to DNA termini; nonspecific linear DNA; and circular DNA [6].
  • YPF1 beta transcripts occur at low levels in all stages of Drosophila development except during oogenesis and early embryogenesis when they increase 25-fold [7].
  • The Ku protein complex is involved in length regulation of Drosophila telomeres [8].

Anatomical context of Irbp

  • A p70-p86 heterodimer, Ku, accounts for the DNA end binding activity in eukaryotic cell extracts [9].
  • We describe a novel 5' to 3' single-strand exonuclease activity exhibited by a Ku preparation purified from a human cell line [10].
  • A Northern analysis using specific cDNA probes showed that Ku poly(A)+ mRNAs are expressed at high levels in Xenopus adult oocyte and testis [11].
  • A clone isolated from a Rhipicephalus appendiculatus salivary gland cDNA library encodes a homologue of the 70-kDa subunit of the mammalian Ku protein, an ATP-dependent DNA helicase [12].

Associations of Irbp with chemical compounds

  • Ku, also known as nuclear Factor IV, is an abundant nuclear DNA-binding protein which requires free DNA ends for the initial interaction with double-stranded DNA (dsDNA) and can bind at multiple sites along dsDNA in an energy-independent manner [13].

Other interactions of Irbp

  • Genetic studies have demonstrated an interaction between the gene (mus309, for mutagen-sensitive) encoding the Drosophila Bloom's syndrome helicase homolog (DmBLM) and the Ku70 gene, which is involved in NHEJ [3].

Analytical, diagnostic and therapeutic context of Irbp

  • Sequence analysis shows that IRBP is related to the 70-kDa subunit of the human Ku autoimmune antigen [5].
  • Southwestern blot experiments demonstrate that, like the Ku protein, the smaller YPF1 subunit binds DNA in the absence of the larger subunit [7].
  • We have used an electrophoretic mobility shift assay to further define the DNA binding properties of the Ku protein [13].
  • Titration of Ku to a fixed amount of any of several target linear dsDNA fragments produced ladders of shifted bands proportional to the length of DNA, confirming the multiple binding activity of Ku and demonstrating its sequence-independent nature [13].
  • The three-dimensional structures of the major part of the Ku heterodimer, representing the DNA-binding core, both free and bound to DNA are known from X-ray crystallography [14].


  1. Sterility of Drosophila with mutations in the Bloom syndrome gene--complementation by Ku70. Kusano, K., Johnson-Schlitz, D.M., Engels, W.R. Science (2001) [Pubmed]
  2. Drosophila IRBP/Ku p70 corresponds to the mutagen-sensitive mus309 gene and is involved in P-element excision in vivo. Beall, E.L., Rio, D.C. Genes Dev. (1996) [Pubmed]
  3. Interplay between Drosophila Bloom's syndrome helicase and Ku autoantigen during nonhomologous end joining repair of P element-induced DNA breaks. Min, B., Weinert, B.T., Rio, D.C. Proc. Natl. Acad. Sci. U.S.A. (2004) [Pubmed]
  4. DNA double-strand-break sensitivity, DNA replication, and cell cycle arrest phenotypes of Ku-deficient Saccharomyces cerevisiae. Barnes, G., Rio, D. Proc. Natl. Acad. Sci. U.S.A. (1997) [Pubmed]
  5. A Drosophila protein homologous to the human p70 Ku autoimmune antigen interacts with the P transposable element inverted repeats. Beall, E.L., Admon, A., Rio, D.C. Proc. Natl. Acad. Sci. U.S.A. (1994) [Pubmed]
  6. DNA binding specificities of YPF1, a Drosophila homolog to the DNA binding subunit of human DNA-dependent protein kinase, Ku. Jacoby, D.B., Wensink, P.C. J. Biol. Chem. (1996) [Pubmed]
  7. Yolk protein factor 1 is a Drosophila homolog of Ku, the DNA-binding subunit of a DNA-dependent protein kinase from humans. Jacoby, D.B., Wensink, P.C. J. Biol. Chem. (1994) [Pubmed]
  8. The Ku protein complex is involved in length regulation of Drosophila telomeres. Melnikova, L., Biessmann, H., Georgiev, P. Genetics (2005) [Pubmed]
  9. Protein-protein and protein-DNA interaction regions within the DNA end-binding protein Ku70-Ku86. Wu, X., Lieber, M.R. Mol. Cell. Biol. (1996) [Pubmed]
  10. 5' to 3' single strand DNA exonuclease activity in a preparation of human Ku protein. Morozov, V.E., Fuller, B.G. IUBMB Life (1999) [Pubmed]
  11. Molecular cloning and sequencing of cDNAs encoding homologues of human Ku70 and Ku80 autoantigen from Xenopus and their expression in various Xenopus tissues. Yagura, T., Sumi, K. Biochim. Biophys. Acta (1999) [Pubmed]
  12. A tick homologue of the human DNA helicase II 70-kDa subunit. Paesen, G.C., Zanotto, P.M., Nuttall, P.A. Biochim. Biophys. Acta (1996) [Pubmed]
  13. Binding of Ku protein to DNA. Measurement of affinity for ends and demonstration of binding to nicks. Blier, P.R., Griffith, A.J., Craft, J., Hardin, J.A. J. Biol. Chem. (1993) [Pubmed]
  14. The 3D solution structure of the C-terminal region of Ku86 (Ku86CTR). Harris, R., Esposito, D., Sankar, A., Maman, J.D., Hinks, J.A., Pearl, L.H., Driscoll, P.C. J. Mol. Biol. (2004) [Pubmed]
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