Structural Biology

Biography

Biography: Christian Biertümpfel

Abstract

Several DNA repair and maintenance pathways depend on the correct and efficient processing of DNA intermediates by structure-specific nucleases. Human Holliday junction resolvase GEN1 seems to be an enzyme of last resort for recognizing and cleaving a specific range of DNA structures. The crystal structure of human GEN1 in complex with Holliday junction DNA pinpointed to a crucial role of the chromodomain for efficient DNA recognition and cleavage. We further characterized different DNA-binding modes of GEN1 using biochemical methods in combination with structure-guided mutagenesis. The analysis highlights the importance of the arch region to distinguish between different DNA substrates. In addition, we identified a cluster of positive amino acids shadowing the chromodomain to assist the enzyme for robust DNA recognition. Moreover, we directly show that GEN1 operates as a monomer with 5’ flap DNA and as a dimer in complex with DNA four-way junctions, which is a unique feature in the Rad2/XPG nuclease family. This linked cleavage mechanism ensures that DNA junctions are resolved in a strictly symmetric manner without altering DNA information. GEN1’s DNA recognition features make it a versatile tool for DNA processing and for maintaining genome integrity.

Figure: Holliday junction resolvase GEN1 is a monomer in solution and thus, cleavage competent for 5’ flap substrates. However, it can only cleave DNA four-way junctions by forming an active nuclease dimer.

References:

1. Lee SH, Princz LN, Klügel MF, Habermann B, Pfander B, Biertümpfel C. (2015). Human Holliday junction resolvase GEN1 uses a chromodomain for efficient DNA recognition and cleavage. Elife, 4, e12256.
2. Zhao Y, Gregory MT, Biertümpfel C, Hua YJ, Hanaoka F, Yang W. (2013). Mechanism of somatic hypermutation at the WA motif by human DNA polymerase η. Proc Natl Acad Sci U S A 110, 8146-51.
3. Joyce MG, Kanekiyo M, Xu L, Biertümpfel C, Boyington JC, Moquin S, Shi W, Wu X, Yang Y, Yang ZY, Zhang B, Zheng A, Zhou T, Zhu J, Mascola JR, Kwong PD, Nabel GJ. (2013). Outer domain of HIV-1 gp120: antigenic optimization, structural malleability, and crystal structure with antibody VRC-PG04. J Virol 87, 2294-306.
4. Zhao Y, Biertümpfel C, Gregory MT, Hua YJ, Hanaoka F, Yang W. (2012). Structural basis of human DNA polymerase η-mediated chemoresistance to cisplatin. Proc Natl Acad Sci U S A 109, 7269-74.
5. Hansman GS, Biertümpfel C, Georgiev I, McLellan JS, Chen L, Zhou T, Katayama K, Kwong PD. (2011). Crystal structures of GII.10 and GII.12 norovirus protruding domains in complex with histo-blood group antigens reveal details for a potential site of vulnerability. J Virol 85, 6687-701