The tumor suppressor PTEN is a lipid phosphatase that is found mutated in different types of human cancers. PTEN suppresses cell proliferation by inhibiting the PI3K-Akt signaling pathway at the cell membrane. However, PTEN is also demonstrated to localize in the cell nucleus where it exhibits tumor suppressive activity via a different, unknown mechanism. In this study we report that PTEN also localizes to the nucleolus and that nucleolar PTEN plays an important role in regulating nucleolar homeostasis and maintaining nucleolar morphology. Overexpression of nuclear PTEN in PTEN null cells inhibits Akt phosphorylation and reduces cell size. Knockdown of PTEN in PTEN positive cells leads to nucleolar morphologic changes and an increase in the proportion of cells with a greater number of nucleoli. In addition, knockdown of PTEN in PTEN positive cells increased ribosome biogenesis. These findings expand current understanding of function and relevance of nuclear localized PTEN and provide a foundation for the development of novel therapies targeting PTEN.
- the central and most important part of an object, movement, or group, forming the basis for its activity and growth.
The nucleus’s function is to maintain the integrity of the genes and to control the activities of the cell by regulating gene expression — the nucleus is therefore the control center of the cell.
The nucleus structure is bound by a double membrane called the nuclear envelope.
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Consist of two major components — the small ribosomal subunit which reads the RNA, and the large subunit which joins amino acids to form a polypeptide chain.
- a space or vesicle within the cytoplasm of a cell, enclosed by a membrane and typically containing fluid.
Some functions that the vacuole has is that it Isolates materials that might be harmful or a threat to the cell and Contains waste products.
Vlatokovic N, Boyd MT and Rubbi CP (2014) Nucleolar control of p53: a cellular Achilles' heel and a target for cancer therapy. Cellular and Molecular Life Sciences 71: 771–791.
Lin T, Meng L, Lin T‐C, et al. (2014) Nucleostemin and GNL3L exercise distinct functions in genome protection and ribosome synthesis. Journal of Cell Science 127: 2302–2312.
The nucleus is surrounded by the nuclear membrane
ribosome - small organelles composed of RNA-rich cytoplasmic granules that are sites of protein synthesis.
rough endoplasmic reticulum - (rough ER) a vast system of interconnected, membranous, infolded and convoluted sacks that are located in the cell's cytoplasm (the ER is continuous with the outer nuclear membrane).
ribosomes also export the polypeptide produced to the cytoplasm where it will form a functional protein.
Ribosomes in a cell are located in two regions of the cytoplasm, they are found scattered in the cytoplasm and some are attached to the endoplasmic reticulum and are tiny particles composed with RNA and protein.
Additionally, the 5' cap of the mRNA forms the ribosome binding site.
The tables below summarise the amino acids (and their abbreviations) coded for in the
Proteins destined for the plasma membrane are also manufactured in the RER, so that they can be
readily packaged into membrane-bound vesicles and enter the membrane-transport system.
Ribosomes are comprised of two structural subunits: the large subunit and the small subunit.
A structure like a ribosome is very complex and yet very minute,
which makes a complete understanding of how it works difficult to achieve, however, rapid progress is being made, helped by
The envelope helps to maintain the shape of the nucleus and assists in regulating the flow of molecules into and out of the nucleus through nuclear pores.
- a minute particle consisting of RNA and associated proteins, found in large numbers in the cytoplasm of living cells.
A function that the ribosome has is that they assemble amino acids to form specific proteins and also send genetic messages from the mRNA which are translated into proteins during the DNA translation.
Grob A, Colleran C and McStay B (2014) Construction of synthetic nucleoli in human cells reveals how a major functional nuclear domain is formed and propagated through cell division. Genes and Development 22: 220–230.