Replication origin plasticity, Taylor-made: inhibition vs recruitment of origins under conditions of replication stress.

Among his many contributions to the field of chromosome structure and dynamics, J. Herbert Taylor showed that eukaryotic cells have many more potential replication origins than they use, which they can recruit when replication forks are slowed to complete S-phase in a timely fashion. Thirty years later, his findings raise an important but largely overlooked paradox. Although new data have confirmed his results, a larger body of data has revealed that slowing replication forks activates an S-phase checkpoint cascade that inhibits initiation from unfired origins until the stress is relieved. In this paper, in celebration of Taylor's work published in Chromosoma 30 years ago, I draw attention to this paradox and offer some plausible models to explain how replication stress can both inhibit and recruit new origins. I hope that this essay will stimulate further experimentation into the basis of Taylor's original findings.