Nucleus Structure

The nucleus (plural: nuclei) is found in eukaryotic cells. While most cells have a single nucleus, some cell types do not have a nucleus while others have many nuclei. A cell’s nucleus is a membrane-bound organelle that consists of the nuclear envelope, a double membrane that surrounds and isolates the nuclear contents, and the nuclear matrix which acts like the cytoskeleton and provides support [1,2].

The nucleus contains the cell’s genetic material (chromosomes) and is the primary site of gene expression and DNA replication during cell cycle. The nucleus also contains various proteins such as histones, which form chromosomes.

Within the nucleus is a sub-compartment known as the nucleolus, which is responsible for synthesizing ribosomal RNA (rRNA) and subsequently assembling ribosomes.

Learn more about additional nuclear membrane stains

SYTO stains are cell-permeant stains that exhibit bright fluorescence upon binding to nucleic acids in live and dead cells (Figure 1). These dyes can also stain Gram-positive and Gram-negative bacteria. There are a range of wavelengths available, and each stain has a different fluorescence intensity, binding affinity, and nucleic acid selectivity. It is important to note that SYTO dyes do not exclusively stain the nucleus like DNA-selective dyes, such as DAPI or Hoechst 33342. Cells stained with SYTO dyes generally show cytoplasmic or mitochondrial staining.

The nucleolus is a non-membrane-bound structure found within the nucleus and is the site where ribosomal RNA is transcribed. The SYTO RNASelect Green Fluorescent Cell Stain is a cell-permeant nucleic acid stain that is selective for RNA. When bound to RNA, the RNASelect stain will fluoresce bright green but when bound to DNA, it will weakly fluoresce. The SYTO RNASelect stain can be used to detect nucleoli, and cells may be counterstained with a nuclear stain such as DAPI (Figure 2).

SYTO RNASelect Green Fluorescent Cell Stain can be used in live cells or fixed cells. After live cells have been stained, they may be methanol fixed with a minimal loss of staining pattern. Formaldehyde fixation is not recommended since the staining pattern will be altered.

SYTOX nucleic acid stains are cell-impermeant, high-affinity nucleic acid stains that will cross a compromised membrane but will not cross the membrane of live cells. This makes them useful dead-cell stains. Upon binding nucleic acids, there is a >500-fold increase in fluorescence. SYTOX dead cell stains are available in a variety of colors for multiplexing and colocalization studies in fixed cells. They are also incorporated into several assays for apoptosis and cell viability.

SYTOX stains can be used in various applications. For example, SYTOX Blue and SYTOX Green nucleic acid stains have been used for DNA counterstains for chromosome labeling. They can also be used for Gram-negative and Gram-positive bacterial staining. SYTOX Deep Red nucleic acid stain has been used for single-cell analysis (Figure 3), tissue sections, 3D cell models, and bacteria.

CellLight fluorescent fusion proteins are available for nuclear and nuclear protein labeling. CellLight Nucleus (Figure 4) uses a SV40 nuclear localization sequence (1.0 kDa) for identification and demarcation of the nucleus in live-cell imaging experiments. CellLight Histone (Figure 5) uses a histone 2B sequence (13.7 kDa) to follow the dynamics of chromosomal behavior and is particularly useful for real-time imaging of mitotic cell division.

Introducing CellLight fluorescent proteins involves a simple transfection step using the BacMam technology, and they work like cell stains with minimal toxicity or chemical disruption. These nucleus fusion proteins are compatible with other fluorescent probes for multiplex analysis in live cells, or after formaldehyde fixation for colocalization studies.

Learn more about these and other CellLight fluorescent reagents

Learn more about nucleic acid detection and analysis

References

1. Lusk CP and King MC (2017). Curr Opin Cell Biol. 44:44-50. PMID: 28236735.
2. Pederson T (2011). Cold Spring Harb Perspect Biol. 3(5):a000521. PMID: 20660024.