Journal of Biological Chemistry
Volume 275, Issue 8, 25 February 2000, Pages 5573-5581
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DNA: REPLICATION REPAIR AND RECOMBINATION
The Yeast STM1 Gene Encodes a Purine Motif Triple Helical DNA-binding Protein*

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The formation of triple helical DNA has been evoked in several cellular processes including transcription, replication, and recombination. Using conventional and affinity chromatography, we purified from Saccharomyces cerevisiaewhole-cell extract a 35-kDa protein that avidly and specifically bound a purine motif triplex (with a K d of 61 pm) but not a pyrimidine motif triplex or duplex DNA. Peptide microsequencing identified this protein as the product of theSTM1 gene. Confirmation that Stm1p is a purine motif triplex-binding protein was obtained by electrophoretic mobility shift assays using either bacterially expressed, recombinant Stm1p or whole-cell extracts from stm1Δ yeast. Stm1p has previously been identified as G4p2, a G-quartet nucleic acid-binding protein. This suggests that some proteins actually recognize features shared by G4 DNA and purine motif triplexes, e.g. Hoogsteen hydrogen-bonded guanines. Genetically, the STM1 gene has been identified as a multicopy suppressor of mutations in several genes involved in mitosis (e.g. TOM1,MPT5, and POP2). A possible role for multiplex DNA and its binding proteins in mitosis is discussed.

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*

This work was supported by The Robert A. Welch Foundation Grant G-1199 (to M. W. V. D.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Present address: Dipartimento di Oncologia Biologia e Genetica, Università di Genova, Viale Benedetto XV, 6., 16132 Genova, Italy.