Human DNA polymerase α in binary complex with a DNA:DNA template-primer

Javier Coloma, Robert E. Johnson, Louise Prakash, Satya Prakash, Aneel K. Aggarwal

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

The Polα/primase complex assembles the short RNA-DNA fragments for priming of lagging and leading strand DNA replication in eukaryotes. As such, the Polα polymerase subunit encounters two types of substrates during primer synthesis: an RNA:DNA helix and a DNA:DNA helix. The engagement of the polymerase subunit with the DNA:DNA helix has been suggested as the of basis for primer termination in eukaryotes. However, there is no structural information on how the Polα polymerase subunit actually engages with a DNA:DNA helix during primer synthesis. We present here the first crystal structure of human Polα polymerase subunit in complex with a DNA:DNA helix. Unexpectedly, we find that portion of the DNA:DNA helix in contact with the polymerase is not in a B-form but in a hybrid A-B form. Almost all of the contacts observed previously with an RNA primer are preserved with a DNA primer-with the same set of polymerase residues tracking the sugar-phosphate backbone of the DNA or RNA primer. Thus, rather than loss of specific contacts, the free energy cost of distorting DNA from B-to hybrid A-B form may augur the termination of primer synthesis in eukaryotes.

Original languageEnglish (US)
Article number23784
JournalScientific reports
Volume6
DOIs
StatePublished - Apr 1 2016

ASJC Scopus subject areas

  • General

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