TY - JOUR
T1 - Redundant and differential regulation of multiple licensing factors ensures prevention of re-replication in normal human cells
AU - Sugimoto, Nozomi
AU - Yoshida, Kazumasa
AU - Tatsumi, Yasutoshi
AU - Yugawa, Takashi
AU - Narisawa-Saito, Mako
AU - Waga, Shou
AU - Kiyono, Tohru
AU - Fujita, Masatoshi
PY - 2009/4/15
Y1 - 2009/4/15
N2 - When human cells enter S-phase, overlapping differential inhibitory mechanisms downregulate the replication licensing factors ORC1, CDC6 and Cdt1. Such regulation prevents rereplication so that deregulation of any individual factor alone would not be expected to induce overt re-replication. However, this has been challenged by the fact that overexpression of Cdt1 or Cdt1+CDC6 causes re-replication in some cancer cell lines. We thought it important to analyze licensing regulations in human non-cancerous cells that are resistant to Cdt1-induced re-replication and examined whether simultaneous deregulation of these licensing factors induces re-replication in two such cell lines, including human fibroblasts immortalized by telomerase. Individual overexpression of either Cdt1, ORC1 or CDC6 induced no detectable re-replication. However, with Cdt1+ORC1 or Cdt1+CDC6, some re-replication was detectable and coexpression of Cdt1+ORC1+CDC6 synergistically acted to give strong re-replication with increased mini-chromosome maintenance (MCM) loading. Coexpression of ORC1+CDC6 was without effect. These results suggest that, although Cdt1 regulation is the key step, differential regulation of multiple licensing factors ensures prevention of re-replication in normal human cells. Our findings also show for the first time the importance of ORC1 regulation for prevention of re-replication.
AB - When human cells enter S-phase, overlapping differential inhibitory mechanisms downregulate the replication licensing factors ORC1, CDC6 and Cdt1. Such regulation prevents rereplication so that deregulation of any individual factor alone would not be expected to induce overt re-replication. However, this has been challenged by the fact that overexpression of Cdt1 or Cdt1+CDC6 causes re-replication in some cancer cell lines. We thought it important to analyze licensing regulations in human non-cancerous cells that are resistant to Cdt1-induced re-replication and examined whether simultaneous deregulation of these licensing factors induces re-replication in two such cell lines, including human fibroblasts immortalized by telomerase. Individual overexpression of either Cdt1, ORC1 or CDC6 induced no detectable re-replication. However, with Cdt1+ORC1 or Cdt1+CDC6, some re-replication was detectable and coexpression of Cdt1+ORC1+CDC6 synergistically acted to give strong re-replication with increased mini-chromosome maintenance (MCM) loading. Coexpression of ORC1+CDC6 was without effect. These results suggest that, although Cdt1 regulation is the key step, differential regulation of multiple licensing factors ensures prevention of re-replication in normal human cells. Our findings also show for the first time the importance of ORC1 regulation for prevention of re-replication.
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U2 - 10.1242/jcs.041889
DO - 10.1242/jcs.041889
M3 - Article
C2 - 19339550
AN - SCOPUS:66849093505
VL - 122
SP - 1184
EP - 1191
JO - The Quarterly journal of microscopical science
JF - The Quarterly journal of microscopical science
SN - 0021-9533
IS - 8
ER -