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Decision-making during NHEJ: a network of interactions in human Pol? implicated in substrate recognition and end-bridging.


ABSTRACT: Human Pol? is a DNA polymerase belonging to the X family that has been implicated in the non-homologous end-joining (NHEJ) pathway during repair of double-strand breaks in DNA. Loop1 is a flexible piece of Pol? which has a critical role during terminal transferase and end-joining activities: it acts as a pseudo-template when the template strand is discontinuous or unavailable, whilst diffusing away if present to avoid steric clashes. Mutational analysis and inspection of the 3D structures available allowed us to identify a network of residues in charge of sensing the presence or absence of discontinuities in the template strand, which will in turn determine the final position adopted by Loop1. This network is formed by the previously uncharacterized thumb mini-loop (NSH motif) and the positively charged helix N, which contribute to the correct positioning of Loop1 and to juxtapose the discontinuous template strand during NHEJ of incompatible ends. Accordingly, single mutation of specific conserved residues in these motifs, whilst irrelevant in most of the cases for gap filling, largely affected terminal transferase and end-joining activities. Other point mutations in the 'hinges' of Loop1, such as residues Phe385 or Phe389, corroborated the flexibility requirements of this motif.

SUBMITTER: Martin MJ 

PROVIDER: S-EPMC4081086 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature

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Decision-making during NHEJ: a network of interactions in human Polμ implicated in substrate recognition and end-bridging.

Martin Maria Jose MJ   Blanco Luis L  

Nucleic acids research 20140530 12


Human Polμ is a DNA polymerase belonging to the X family that has been implicated in the non-homologous end-joining (NHEJ) pathway during repair of double-strand breaks in DNA. Loop1 is a flexible piece of Polμ which has a critical role during terminal transferase and end-joining activities: it acts as a pseudo-template when the template strand is discontinuous or unavailable, whilst diffusing away if present to avoid steric clashes. Mutational analysis and inspection of the 3D structures availa  ...[more]

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