Stimulation of DNA Polymerase α Activity by Microtubule-Associated Proteins

Masaki Shioda, Koji Okuhara, Hiromu Murofushi, Akiko Mori, Hikoichi Sakai, Kimiko Murakami-Murofushi, Motoshi Suzuki, Shonen Yoshida

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Abstract

Microtubule-associated protein 2 (MAP2) isolated from porcine brains stimulated the activity of DNA polymerase α immunopurified from calf thymus or human lymphoma cells, in a dose-dependent manner. This stimulation was pronounced when activated DNA or poly(dA)•(dT)10 was used as the template-primer. DNA polymerase α bound to a MAP2-immobilized column, whereas preincubation of the enzyme with unbound MAP2 prevented binding to the column. These events suggested that a physical binding occurred between the polymerase and MAP2. Kinetic analyses revealed that MAP2 decreased the Km value of the polymerase for deoxyribonucleotides, irrespective of the species of template-primer. A concomitant increase in Vmax was observed; however, the extent of the increase depended on the species of template-primer. MAP2 also decreased the Km value of the polymerase for template-primers when activated DNA of poly(dA)•(dT)10 was used as the template-primer. Product analyses showed that MAP2 did not significantly alter the processivity of the polymerase and the increment of Vmax is considered to be due to an increase in the frequency of initiation of DNA synthesis. The stimulation by MAP2 occurred specifically in the activity of DNA polymerase α, but not DNA polymerases β, γ, and I from Escherichia coli. Other MAPs, tau and 190-kDa MAP, could substitute for MAP2. Thus, the specific stimulation of DNA polymerase α by MAPs supports the notion of a possible involvement of MAPs or MAP-like proteins in DNA replication, in vivo.

Original languageEnglish
Pages (from-to)11403-11412
Number of pages10
JournalBiochemistry
Volume30
Issue number48
DOIs
Publication statusPublished - 01-12-1991
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Biochemistry

Cite this

Shioda, M., Okuhara, K., Murofushi, H., Mori, A., Sakai, H., Murakami-Murofushi, K., Suzuki, M., & Yoshida, S. (1991). Stimulation of DNA Polymerase α Activity by Microtubule-Associated Proteins. Biochemistry, 30(48), 11403-11412. https://doi.org/10.1021/bi00112a006