RESUMEN

The structure of the multisubunit yeast DNA polymerase epsilon (Pol epsilon) was determined to 20-A resolution using cryo-EM and single-particle image analysis. A globular domain comprising the catalytic Pol2 subunit is flexibly connected to an extended structure formed by subunits Dpb2, Dpb3 and Dpb4. Consistent with the reported involvement of the latter in interaction with nucleic acids, the Dpb portion of the structure directly faces a single cleft in the Pol2 subunit that seems wide enough to accommodate double-stranded DNA. Primer-extension experiments reveal that Pol epsilon processivity requires a minimum length of primer-template duplex that corresponds to the dimensions of the extended Dpb structure. Together, these observations suggest a mechanism for interaction of Pol epsilon with DNA that might explain how the structure of the enzyme contributes to its intrinsic processivity.

Asunto(s)

ADN Polimerasa II/química , ADN Polimerasa II/ultraestructura , Saccharomyces cerevisiae/enzimología , Catálisis , Microscopía por Crioelectrón , ARN Helicasas DEAD-box , ADN Polimerasa II/metabolismo , ADN de Hongos/química , ADN de Hongos/metabolismo , ADN de Hongos/ultraestructura , Modelos Moleculares , Unión Proteica , Estructura Cuaternaria de Proteína , Estructura Terciaria de Proteína , Subunidades de Proteína/química , Subunidades de Proteína/metabolismo , ARN Helicasas/química , ARN Helicasas/metabolismo , ARN Helicasas/ultraestructura , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/ultraestructura