Related Experiment Video
Updated: Jun 30, 2026
11:19
Spatiotemporal Analysis of Cytokinetic Events in Fission Yeast
Published on: February 20, 2017
Speedy/Ringo C regulates S and G2 phase progression in human cells
1Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520-8024, USA.
Cell Cycle (Georgetown, Tex.)
|September 20, 2008
Summary
Speedy/Ringo C proteins regulate cell cycle progression. This study shows Speedy/Ringo C promotes cell division by shortening G2 phase and enhancing S phase progression in human cells.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Cyclin-dependent kinases (CDKs) are key regulators of the cell cycle.
- Speedy/Ringo (S/R) proteins represent a distinct class of CDK activators.
- The specific functions of mammalian S/R protein family members are largely unknown.
Purpose of the Study:
- To investigate the cell cycle roles of human Speedy/Ringo C.
- To determine the impact of Speedy/Ringo C on cell cycle progression in HEK293 cells.
Main Methods:
- RNA interference (RNAi) for Speedy/Ringo C down-regulation.
- Ectopic expression of Speedy/Ringo C.
- Double thymidine arrest and release experiments.
- A novel three-color Fluorescence-Activated Cell Sorting (FACS) protocol to measure G2 phase length.
Main Results:
- Speedy/Ringo C down-regulation by RNAi delayed S and G2 phase progression.
- Ectopic Speedy/Ringo C expression reduced S and G2/M populations and promoted late S phase progression.
- Speedy/Ringo C suppression prolonged G2 phase by ~30 min; ectopic expression shortened it by ~25 min.
- Overexpression of Speedy/Ringo C disrupted the G2 DNA damage checkpoint, increased cell death, and caused a G1-to-S transition delay.
Conclusions:
- CDK-Speedy/Ringo C complexes positively regulate cell cycle progression.
- Speedy/Ringo C plays a critical role in late S and G2 phase progression.
- Speedy/Ringo C influences G2 phase length and the DNA damage checkpoint.
Related Concept Videos
01:23Negative Regulator Molecules
Positive regulators allow a cell to advance through cell cycle checkpoints. Negative regulators have an equally important role as they terminate a cell’s progression through the cell cycle—or pause it—until the cell meets specific criteria.
01:28The Cell Cycle Control System
The cell cycle regulation directs how a cell proceeds from one phase to the next and begins mitosis. The cell cycle control system includes intracellular regulatory molecules and external triggers. They provide "stop" or "advance" signals and operate at specific cell cycle stages termed checkpoints to ensure that a particular process is completed before the cell advances to the next phase.
Cyclins and cyclin-dependent kinases (Cdks) are the primary cell cycle regulators and function at the cell...
Cyclins and cyclin-dependent kinases (Cdks) are the primary cell cycle regulators and function at the cell...
02:11The Cell Cycle Control System
The cell cycle is an organized set of events that leads the cell to divide into two daughter cells, each containing chromosomes identical to the parent cell. It is the cell cycle that leads to the formation of an entire organism from a single-cell zygote. Besides, cell division also functions in the renewal or repair of tissues in adult multicellular eukaryotes. For example, in the bone marrow, the stem cells divide to form new blood cells. Although essential for several functions, cell...
02:11The Cell Cycle Control System
The cell cycle is an organized set of events that leads the cell to divide into two daughter cells, each containing chromosomes identical to the parent cell. It is the cell cycle that leads to the formation of an entire organism from a single-cell zygote. Besides, cell division also functions in the renewal or repair of tissues in adult multicellular eukaryotes. For example, in the bone marrow, the stem cells divide to form new blood cells. Although essential for several functions, cell...
02:15The Contractile Ring
Contractile rings are composed of microfilaments and are responsible for separating the daughter cells during cytokinesis. Contractile ring assembly proceeds along with other cell cycle events; however, very few mechanistic details are known about the timing and coordination of the contractile rings with the cell cycle.
A small GTPase, RhoA, controls the function and assembly of the contractile ring. RhoA belongs to the Ras superfamily of proteins. The activation of formins by RhoA promotes...
A small GTPase, RhoA, controls the function and assembly of the contractile ring. RhoA belongs to the Ras superfamily of proteins. The activation of formins by RhoA promotes...
02:34Inhibition of Cdk Activity
The orderly progression of the cell cycle depends on the activation of Cdk protein by binding to its cyclin partner. However, the cell cycle must be restricted when undergoing abnormal changes. Most cancers correlate to the deregulated cell cycle, and since Cdks are a central component of the cell cycle, Cdk inhibitors are extensively studied to develop anticancer agents. For instance, cyclin D associates with several Cdks, such as Cdk 4/6, to form an active complex. The cyclin D-Cdk4/6 complex...