Proliferating cell nuclear antigen (PCNA) may function as a double homotrimer complex in the mammalian cell |
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Authors: | Naryzhny Stanislav N Zhao Helen Lee Hoyun |
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Affiliation: | Department of Research, Northeastern Ontario Regional Cancer Centre, Sudbury, Ontario P3E 5J1, Canada. |
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Abstract: | The diverse function of proliferating cell nuclear antigen (PCNA) may be regulated by interactions with different protein partners. Interestingly, the binding sites for all known PCNA-associating proteins are on the outer surface or the C termini ("front") sides of the PCNA trimer. Using cell extracts and purified human PCNA protein, we show here that two PCNA homotrimers form a back-to-back doublet. Mutation analysis suggests that the Arg-5 and Lys-110 residues on the PCNA back side are the contact points of the two homotrimers in the doublet. Furthermore, short synthetic peptides encompassing either Arg-5 or Lys-110 inhibit double trimer formation. We also found that a PCNA double trimer, but not a homotrimer alone, can simultaneously accommodate chromatin assembly factor-1 and polymerase delta. Together, our data supports a model that chromatin remodeling by chromatin assembly factor-1 (and, possibly, many other cellular activities) are tightly coupled with DNA replication (and repair) through a PCNA double trimer complex. |
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