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Key protein in eukaryotic replication occurs in distinct populations

January 2016. DNA replication is a fundamental cellular process that precedes cell division. A key protein in eukaryotic replication is proliferating cell nuclear antigen (PCNA), a 30 kDa protein which acts as DNA scaffold for many essential proteins involved in replication that are unable to bind to DNA directly. At the core of the replication machinery, PCNA forms a sliding clamp around the DNA. PCNA is usually ubiquitously distributed in the nucleus but during replication assembles into microscopically visible clusters of varying sizes called replication foci. Characteristic patterns of these clusters are found in the different stages of DNA replication.

A team of scientists from the Goethe University Frankfurt and the Max-Delbrück Center for Molecular Medicine in Berlin studied the mobility of PCNA in living mammalian cells using single-particle tracking in combination with photoactivated-localization microscopy (sptPALM) and found two distinct populations of PCNA. The first population, which is only present in cells with active DNA replication, showed slow diffusion and was found to be located in replication foci. The second population showed fast diffusion and represents the nucleoplasmic pool of unbound PCNA not involved in DNA replication. The ratio of these two populations remained constant throughout different stages of S-phase. A fraction of molecules in both populations showed spatially constrained mobility. More ...


Mike Heilemann
Institute of Physical and Theoretical Chemistry
Goethe University Frankfurt
Max von Laue Straße 9
60438 Frankfurt, Germany

Zessin PJM, Sporbert A, Heilemann M (2016) PCNA appears in two populations of slow and fast diffusion with a constant ratio throughout S-phase in replicating mammalian cells. Scientific Reports 6:18779. Link