Title

Phosphorylation of Iqg1 by Cyclin Dependent Kinase (Cdc28) Temporally Regulates Actin Ring Formation

Presenter Information

Daniel Miller

Department

Biological Sciences

Major

Biological Sciences

Research Advisor

Shannon, Katie

Advisor's Department

Biological Sciences

Abstract

Cytokinesis is the final step in mitosis when the cell separates the cytoplasm by contracting a ring composed of filamentous actin (F-actin) and type II myosin. Iqg1, an IQGAP1 homolog, is an essential scaffolding protein in budding yeast (S. cerevisiae) required for actin recruitment, and contraction of the actomyosin ring. Actin is recruited by the calponin homology domain (CHD) late in anaphase after Iqg1 is localized to the bud neck. Four perfect consensus sites for the cyclin-dependent kinase Cdc28 were identified flanking the CHD, which lead to the model that Cdc28 phosphorylation of Iqg1 negatively regulates F-actin binding until it is further modified during late anaphase. To test this model the four consensus sites were mutated into a non-phosphorylatable form (A4) and a phosphomimetic form (E4). Our hypothesis is that mutants that cannot be phosphorylated will form actin rings early and disassemble them late, while the phosphomimetic mutant will form actin rings late or not at all. The A4 mutant shows a significant cytokinesis defect, and preliminary immunofluorescences data indicates actin ring formation occurs 20 minutes early, in cells that have not yet completed mitosis.

Biography

Daniel is a graduating senior in the Biological Sciences department. He has been a member of Phi Sigma for two years and a member of Sigma Pi for four years. He was a member of IGEM for a year and left to research in Dr. Katie Shannon's lab. He has researched in her lab for a year and plans on staying at Missouri S&T for graduate studies.

Research Category

Sciences

Presentation Type

Oral Presentation

Document Type

Presentation

Location

Turner Room

Presentation Date

10 Apr 2012, 10:00 am - 10:30 am

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Apr 10th, 10:00 AM Apr 10th, 10:30 AM

Phosphorylation of Iqg1 by Cyclin Dependent Kinase (Cdc28) Temporally Regulates Actin Ring Formation

Turner Room

Cytokinesis is the final step in mitosis when the cell separates the cytoplasm by contracting a ring composed of filamentous actin (F-actin) and type II myosin. Iqg1, an IQGAP1 homolog, is an essential scaffolding protein in budding yeast (S. cerevisiae) required for actin recruitment, and contraction of the actomyosin ring. Actin is recruited by the calponin homology domain (CHD) late in anaphase after Iqg1 is localized to the bud neck. Four perfect consensus sites for the cyclin-dependent kinase Cdc28 were identified flanking the CHD, which lead to the model that Cdc28 phosphorylation of Iqg1 negatively regulates F-actin binding until it is further modified during late anaphase. To test this model the four consensus sites were mutated into a non-phosphorylatable form (A4) and a phosphomimetic form (E4). Our hypothesis is that mutants that cannot be phosphorylated will form actin rings early and disassemble them late, while the phosphomimetic mutant will form actin rings late or not at all. The A4 mutant shows a significant cytokinesis defect, and preliminary immunofluorescences data indicates actin ring formation occurs 20 minutes early, in cells that have not yet completed mitosis.