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Blood, 15 August 2008, Vol. 112, No. 4, pp. 1413-1423.
Prepublished online as a Blood First Edition Paper on June 4, 2008; DOI 10.1182/blood-2007-07-104257.
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NEOPLASIA
Up-regulation of WRN and DNA ligase III in chronic myeloid leukemia: consequences for the repair of DNA double-strand breaks
Annahita Sallmyr1,
Alan E. Tomkinson1, and
Feyruz V. Rassool1
1 Department of Radiation Oncology and Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore
Expression of oncogenic BCR-ABL in chronic myeloid leukemia (CML) results in increased reactive oxygen species (ROS) that in turn cause increased DNA damage, including DNA double-strand breaks (DSBs). We have previously shown increased error-prone repair of DSBs by nonhomologous end-joining (NHEJ) in CML cells. Recent reports have identified alternative NHEJ pathways that are highly error prone, prompting us to examine the role of the alternative NHEJ pathways in BCR-ABL–positive CML. Importantly, we show that key proteins in the major NHEJ pathway, Artemis and DNA ligase IV, are down-regulated, whereas DNA ligase III , and the protein deleted in Werner syndrome, WRN, are up-regulated. DNA ligase III and WRN form a complex that is recruited to DSBs in CML cells. Furthermore, "knockdown" of either DNA ligase III or WRN leads to increased accumulation of unrepaired DSBs, demonstrating that they contribute to the repair of DSBs. These results indicate that altered DSB repair in CML cells is caused by the increased activity of an alternative NHEJ repair pathway, involving DNA ligase III and WRN. We suggest that, although the repair of ROS-induced DSBs by this pathway contributes to the survival of CML cells, the resultant genomic instability drives disease progression.

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A. Kotnis, L. Du, C. Liu, S. W Popov, and Q. Pan-Hammarstrom
Non-homologous end joining in class switch recombination: the beginning of the end
Phil Trans R Soc B,
March 12, 2009;
364(1517):
653 - 665.
[Abstract]
[Full Text]
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