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STN1-POLA2 interaction provides a basis for primase-pol α stimulation by human STN1.

TitleSTN1-POLA2 interaction provides a basis for primase-pol α stimulation by human STN1.
Publication TypeJournal Article
Year of Publication2017
AuthorsGanduri S, Lue NF
JournalNucleic Acids Res
Volume45
Issue16
Pagination9455-9466
Date Published2017 Sep 19
ISSN1362-4962
KeywordsBinding Sites, DNA, DNA Polymerase I, DNA Primase, Humans, Point Mutation, Protein Domains, Protein Subunits, Telomere-Binding Proteins
Abstract

The CST (CTC1-STN1-TEN1) complex mediates critical functions in maintaining telomere DNA and overcoming genome-wide replication stress. A conserved biochemical function of the CST complex is its primase-Pol α (PP) stimulatory activity. In this report, we demonstrate the ability of purified human STN1 alone to promote PP activity in vitro. We show that this regulation is mediated primarily by the N-terminal OB fold of STN1, but does not require the DNA-binding activity of this domain. Rather, we observed a strong correlation between the PP-stimulatory activity of STN1 variants and their abilities to bind POLA2. Remarkably, the main binding target of STN1 in POLA2 is the latter's central OB fold domain. In the substrate-free structure of PP, this domain is positioned so as to block nucleic acid entry to the Pol α active site. Thus the STN1-POLA2 interaction may promote the necessary conformational change for nucleic acid delivery to Pol α and subsequent DNA synthesis. A disease-causing mutation in human STN1 engenders a selective defect in POLA2-binding and PP stimulation, indicating that these activities are critical for the in vivo function of STN1. Our findings have implications for the molecular mechanisms of PP, STN1 and STN1-related molecular pathology.

DOI10.1093/nar/gkx621
Alternate JournalNucleic Acids Res
PubMed ID28934486
PubMed Central IDPMC5766158
Grant ListR01 GM107287 / GM / NIGMS NIH HHS / United States

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