IQGAP1 translocates to the nucleus in early S-phase and contributes to cell cycle progression after DNA replication arrest

Michael Johnson, Manisha Sharma, Mariana G. Brocardo, Beric R. Henderson

Research output: Contribution to journalArticleResearchpeer-review

Abstract

IQGAP1 is a plasma membrane-associated protein and an important regulator of the actin cytoskeleton, contributing to cell migration, polarity and adhesion. In this study, we demonstrate the nuclear translocation of IQGAP1 using confocal microscopy and cell fractionation. Moreover, we identify a specific pool of IQGAP1 that accumulates in the nucleus during late G1-early S phase of the cell cycle. The nuclear targeting of IQGAP1 was facilitated by N- and C-terminal sequences, and its ability to slowly shuttle between nucleus and cytoplasm/membrane was partly regulated by the CRM1 export receptor. The inhibition of GSK-3β also stimulated nuclear localization of IQGAP1. The dramatic nuclear accumulation of IQGAP1 observed when cells were arrested in G1/S phase suggested a possible role in cell cycle regulation. In support of this, we used immunoprecipitation assays to show that the nuclear pool of IQGAP1 in G1/S-arrested cells associates with DNA replication complex factors RPA32 and PCNA. More important, the siRNA-mediated silencing of IQGAP1 significantly delayed cell cycle progression through S phase and G2/M in NIH 3T3 cells released from thymidine block. Our findings reveal an unexpected regulatory pathway for IQGAP1, and show that a pool of this cytoskeletal regulator translocates into the nucleus in late G1/early S phase to stimulate DNA replication and progression of the cell cycle.

LanguageEnglish
Pages65-73
Number of pages9
JournalInternational Journal of Biochemistry and Cell Biology
Volume43
Issue number1
DOIs
Publication statusPublished - Jan 2011
Externally publishedYes

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DNA Replication
S Phase
Cell Cycle
Cells
DNA
Cell Fractionation
NIH 3T3 Cells
Cell Polarity
Confocal microscopy
Proliferating Cell Nuclear Antigen
G1 Phase
Cell membranes
Fractionation
Actin Cytoskeleton
Immunoprecipitation
Cell Adhesion
Confocal Microscopy
Thymidine
Small Interfering RNA
Cell Movement

Cite this

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title = "IQGAP1 translocates to the nucleus in early S-phase and contributes to cell cycle progression after DNA replication arrest",
abstract = "IQGAP1 is a plasma membrane-associated protein and an important regulator of the actin cytoskeleton, contributing to cell migration, polarity and adhesion. In this study, we demonstrate the nuclear translocation of IQGAP1 using confocal microscopy and cell fractionation. Moreover, we identify a specific pool of IQGAP1 that accumulates in the nucleus during late G1-early S phase of the cell cycle. The nuclear targeting of IQGAP1 was facilitated by N- and C-terminal sequences, and its ability to slowly shuttle between nucleus and cytoplasm/membrane was partly regulated by the CRM1 export receptor. The inhibition of GSK-3β also stimulated nuclear localization of IQGAP1. The dramatic nuclear accumulation of IQGAP1 observed when cells were arrested in G1/S phase suggested a possible role in cell cycle regulation. In support of this, we used immunoprecipitation assays to show that the nuclear pool of IQGAP1 in G1/S-arrested cells associates with DNA replication complex factors RPA32 and PCNA. More important, the siRNA-mediated silencing of IQGAP1 significantly delayed cell cycle progression through S phase and G2/M in NIH 3T3 cells released from thymidine block. Our findings reveal an unexpected regulatory pathway for IQGAP1, and show that a pool of this cytoskeletal regulator translocates into the nucleus in late G1/early S phase to stimulate DNA replication and progression of the cell cycle.",
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IQGAP1 translocates to the nucleus in early S-phase and contributes to cell cycle progression after DNA replication arrest. / Johnson, Michael; Sharma, Manisha; Brocardo, Mariana G.; Henderson, Beric R.

In: International Journal of Biochemistry and Cell Biology, Vol. 43, No. 1, 01.2011, p. 65-73.

Research output: Contribution to journalArticleResearchpeer-review

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