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Cyclins: A large family of regulatory proteins that function as accessory subunits to a variety of Cyclin-dependent kinases. They generally function as Enzyme activators that drive the Cell cycle through transitions between phases. A subset of cyclins may also function as transcriptional regulators.

Positive Regulator Molecules

JoVE 10763

To consistently produce healthy cells, the cell cycle—the process that generates daughter cells—must be precisely regulated.

Internal regulatory checkpoints ensure that a cell’s size, energy reserves, and DNA quality and completeness are sufficient to advance through the cell cycle. At these checkpoints, positive and negative regulators promote or inhibit a cell’s continuation through the cell cycle. Positive regulators include two protein groups that allow cells to pass through regulatory checkpoints: cyclins and cyclin-dependent kinases (CDKs). These proteins are present in eukaryotes, ranging from yeast to humans. Cyclins can be categorized as G1, G1/S, S, or M cyclins based on the cell cycle phase or transition they are most involved in. Generally, levels of a given cyclin are low during most of the cell cycle but abruptly increase at the checkpoint they most contribute to (G1 cyclins are an exception, as they are required throughout the cell cycle). The cyclin is then degraded by enzymes in the cytoplasm and its levels decline. Meanwhile, cyclins needed for the next checkpoints accumulate. To regulate the cell cycle, cyclins must be bound to a Cyclin-dependent kinase (CDK)—a type of enzyme that attaches a phosphate group to modify the activity of a target protein.

 Core: Biology

Cell Division - Student Protocol

JoVE 10572

Observing the Cell Cycle in a Root Tip
Hypotheses: The experimental hypothesis is that in root tips slices that have been treated with nocodazole, a chemical that interferes with microtubular polymerization, all of the cells will be arrested at the same stage of the cell cycle and that in untreated onion tip slices all of the different stages of the…

 Lab Bio

An Introduction to Cell Division

JoVE 5640

Cell division is the process by which a parent cell divides and gives rise to two or more daughter cells. It is a means of reproduction for single-cell organisms. In multicellular organisms, cell division contributes to growth, development, repair, and the generation of reproductive cells (sperms and eggs). Cell division is a tightly regulated process, and aberrant cell…

 Cell Biology

Rapid Detection of Neurodevelopmental Phenotypes in Human Neural Precursor Cells (NPCs)

1Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, 2Center for Advanced Biotechnology and Medicine, Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, 3The Child Health Institute of NJ, Department of Obstetrics, Gynecology, and Reproductive Services, Rutgers Robert Wood Johnson Medical School, 4The Child Health Institute of NJ, Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, 5Department of Genetics, Rutgers University

JoVE 56628

 Developmental Biology
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