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-Structure paper
タイトル | Flexibility and Distributive Synthesis Regulate RNA Priming and Handoff in Human DNA Polymerase α-Primase. |
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ジャーナル・号・ページ | J Mol Biol, Vol. 435, Issue 24, Page 168330, Year 2023 |
掲載日 | 2023年12月15日 |
著者 | John J Cordoba / Elwood A Mullins / Lauren E Salay / Brandt F Eichman / Walter J Chazin / |
PubMed 要旨 | DNA replication in eukaryotes relies on the synthesis of a ∼30-nucleotide RNA/DNA primer strand through the dual action of the heterotetrameric polymerase α-primase (pol-prim) enzyme. Synthesis of ...DNA replication in eukaryotes relies on the synthesis of a ∼30-nucleotide RNA/DNA primer strand through the dual action of the heterotetrameric polymerase α-primase (pol-prim) enzyme. Synthesis of the 7-10-nucleotide RNA primer is regulated by the C-terminal domain of the primase regulatory subunit (PRIM2C) and is followed by intramolecular handoff of the primer to pol α for extension by ∼20 nucleotides of DNA. Here, we provide evidence that RNA primer synthesis is governed by a combination of the high affinity and flexible linkage of the PRIM2C domain and the surprisingly low affinity of the primase catalytic domain (PRIM1) for substrate. Using a combination of small angle X-ray scattering and electron microscopy, we found significant variability in the organization of PRIM2C and PRIM1 in the absence and presence of substrate, and that the population of structures with both PRIM2C and PRIM1 in a configuration aligned for synthesis is low. Crosslinking was used to visualize the orientation of PRIM2C and PRIM1 when engaged by substrate as observed by electron microscopy. Microscale thermophoresis was used to measure substrate affinities for a series of pol-prim constructs, which showed that the PRIM1 catalytic domain does not bind the template or emergent RNA-primed templates with appreciable affinity. Together, these findings support a model of RNA primer synthesis in which generation of the nascent RNA strand and handoff of the RNA-primed template from primase to polymerase α is mediated by the high degree of inter-domain flexibility of pol-prim, the ready dissociation of PRIM1 from its substrate, and the much higher affinity of the POLA1cat domain of polymerase α for full-length RNA-primed templates. |
リンク | J Mol Biol / PubMed:37884206 / PubMed Central |
手法 | EM (単粒子) |
解像度 | 7.41 - 15.38 Å |
構造データ | EMDB-42033: RNA priming complex of Human Polymerase-Alpha-Primase (Conformation 1) EMDB-42034: RNA priming complex of Human polymerase alpha-primase (Conformation 2) EMDB-42035: RNA priming complex of Human Polymerase alpha-primase (Conformation 3) EMDB-42036: Human Polymerase alpha-Primase, polymerase alpha catalytic domain deletion mutant (Conformation 1) EMDB-42037: Human Polymerase alpha-Primase, polymerase alpha catalytic domain deletion mutant (Conformation 2) |
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