Subtle alterations in PCNA-partner interactions severely impair DNA replication and repair.
The robustness of complex biological processes in the face of environmental and genetic perturbations is a key biological trait. However, while robustness has been extensively studied, little is known regarding the fragility of biological processes. Here, we have examined the susceptibility of DNA replication and repair processes mediated by the proliferating cell nuclear antigen (PCNA). Using protein directed evolution, biochemical, and genetic approaches, we have generated and characterized PCNA mutants with increased affinity for several key partners of the PCNA-partner network. We found that increases in PCNA-partner interaction affinities led to severe in vivo phenotypic defects. Surprisingly, such defects are much more severe than those induced by complete abolishment of the respective interactions. Thus, the subtle and tunable nature of these affinity perturbations produced different phenotypic effects than realized with traditional "on-off" analysis using gene knockouts. Our findings indicate that biological systems can be robust to one set of perturbations yet fragile to others.
Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Be'er Sheva, Israel.
Yearit
Y
Fridman
Niv
N
Palgi
Daniel
D
Dovrat
Shay
S
Ben-Aroya
Philip
P
Hieter
Amir
A
Aharoni
D000595:Amino Acid Sequence; D000818:Animals; D004260:DNA Repair; D004261:DNA Replication; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D018809:Proliferating Cell Nuclear Antigen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation
D005656:Fungal Proteins; D018809:Proliferating Cell Nuclear Antigen