The interaction of DNA repair factors ASCC2 and ASCC3 is affected by somatic cancer mutations

Junqiao Jia,Eva Absmeier,Markus T Bohnsack,Philipp Hackert,Markus C Wahl,Nicole Holton,Agnieszka J Pietrzyk-Brzezinska,Katherine E Bohnsack

doi:10.1038/s41467-020-19221-x

Abstract

The ASCC3 subunit of the activating signal co-integrator complex is a dual-cassette Ski2-like nucleic acid helicase that provides single-stranded DNA for alkylation damage repair by the α-ketoglutarate-dependent dioxygenase AlkBH3. Other ASCC components integrate ASCC3/AlkBH3 into a complex DNA repair pathway. We mapped and structurally analyzed interacting ASCC2 and ASCC3 regions. The ASCC3 fragment comprises a central helical domain and terminal, extended arms that clasp the compact ASCC2 unit. ASCC2–ASCC3 interfaces are evolutionarily highly conserved and comprise a large number of residues affected by somatic cancer mutations. We quantified contributions of protein regions to the ASCC2–ASCC3 interaction, observing that changes found in cancers lead to reduced ASCC2–ASCC3 affinity. Functional dissection of ASCC3 revealed similar organization and regulation as in the spliceosomal RNA helicase Brr2. Our results delineate functional regions in an important DNA repair complex and suggest possible molecular disease principles.

Highlights

The ASCC3 subunit of the activating signal co-integrator complex is a dual-cassette Ski2-like nucleic acid helicase that provides single-stranded DNA for alkylation damage repair by the α-ketoglutarate-dependent dioxygenase AlkBH3
Analytical size exclusion chromatography (SEC) showed that ASCC2 interacts with ASCC3NTR (Fig. 1a) but not with ASCC3HR (Fig. 1b), consistent with previous reports[9]
We observed that a large number of ASCC2 and ASCC3 residue substitutions encoded by somatic mutations in cancers map to

Summary

Introduction

The ASCC3 subunit of the activating signal co-integrator complex is a dual-cassette Ski2-like nucleic acid helicase that provides single-stranded DNA for alkylation damage repair by the α-ketoglutarate-dependent dioxygenase AlkBH3. 1234567890():,; The human genome is constantly under assault by endogenous or exogenous DNA damaging agents To ward off these insults, cells have evolved systems to recognize DNA damage, signal its presence and initiate repair processes[1]. Several lines of evidence implicate the human activating signal co-integrator complex (ASCC) in AlkBH3-mediated DNA repair. ASCC1 is cleared from these foci upon DNA alkylation damage and knockout of ASCC1 leads to loss of ASCC2 from the nuclear foci and increased cellular sensitivity to alkylating insults[10] Both ASCC2 and ASCC3 have been linked to various human diseases.

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Conclusion