RT Journal Article
SR Electronic
T1 Regulation of Replicon Size in <em>Xenopus</em> Egg Extracts
JF Science
JO Science
FD American Association for the Advancement of Science
SP 993
OP 995
DO 10.1126/science.275.5302.993
VO 275
IS 5302
A1 Walter, Johannes
A1 Newport, John W.
YR 1997
UL http://science.sciencemag.org/content/275/5302/993.abstract
AB Once a specific number of cells have been produced in the early Xenopus laevis embryo, replicon size during the S phase of the cell cycle increases. Here, it is reported that similar increase in replicon size occurred when the concentration of nuclei in replication-competent Xenopus egg extracts exceeded a critical threshold. In this system, the origin recognition complex (ORC) did not become stoichiometrically limiting for initiation, and similar amounts of this complex bound to chromatin regardless of replicon size. These data suggest that in early development, an unidentified factor controls how many preformed ORC-DNA complexes initiate DNA replication.