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Involvement of human ORC and TRF2 in pre‐replication complex assembly at telomeres
Author(s) -
Tatsumi Yasutoshi,
Ezura Kai,
Yoshida Kazumasa,
Yugawa Takashi,
NarisawaSaito Mako,
Kiyono Tohru,
Ohta Satoshi,
Obuse Chikashi,
Fujita Masatoshi
Publication year - 2008
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1111/j.1365-2443.2008.01224.x
Subject(s) - telomere , biology , gene silencing , telomere binding protein , microbiology and biotechnology , origin recognition complex , rna interference , chromatin immunoprecipitation , chromatin , dna replication , dna binding protein , genetics , dna , gene , transcription factor , gene expression , eukaryotic dna replication , rna , promoter
The origin recognition complex (ORC) binds to replication origins to regulate the cell cycle‐dependent assembly of pre‐replication complexes (pre‐RCs). We have found a novel link between pre‐RC assembly regulation and telomere homeostasis in human cells. Biochemical analyses showed that human ORC binds to TRF2, a telomere sequence‐binding protein that protects telomeres and functions in telomere length homeostasis, via the ORC1 subunit. Immunostaining further revealed that ORC and TRF2 partially co‐localize in nuclei, whereas chromatin immunoprecipitation analyses confirmed that pre‐RCs are assembled at telomeres in a cell cycle‐dependent manner. Over‐expression of TRF2 stimulated ORC and MCM binding to chromatin and RNAi‐directed TRF2 silencing resulted in reduced ORC binding and pre‐RC assembly at telomeres. As expected from previous reports, TRF2 silencing induced telomere elongation. Interestingly, ORC1 silencing by RNAi weakened the TRF2 binding as well as the pre‐RC assembly at telomeres, suggesting that ORC and TRF2 interact with each other to achieve stable binding. Furthermore, ORC1 silencing also resulted in modest telomere elongation. These data suggest that ORC might be involved in telomere homeostasis in human cells.