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
Date Published2017 Sep 19
KeywordsBinding Sites, DNA, DNA Polymerase I, DNA Primase, Humans, Point Mutation, Protein Domains, Protein Subunits, Telomere-Binding Proteins

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.

Alternate JournalNucleic Acids Res
PubMed ID28934486
PubMed Central IDPMC5766158
Grant ListR01 GM107287 / GM / NIGMS NIH HHS / United States

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