A person has tens of trillions of cells. When it comes to cells, as if the cells we imagine dating from, the cells of all kinds of organisms are basically kept within a limited size range, so why don’t cells grow indefinitely? According to a new study published in the journal Science by Stanford University scholars, the way cells control their size is incredibly simple. Scientists have found that cells grow in size, but the protein sinlets that inhibit cell division in cells do not grow in the same proportion, so the concentration drops, unable to inhibit the cell’s ambition to split in two, so the size of the cell can grow to the ceiling!
This mechanism is really strange and simple!
It’s really interesting to think about it. There are so many organelles in the cells that there are so many important physiological reactions every day that the image points say live like a microscopic factory. There are laws in the factory from one process to another, and it’s not like a little bit of a big one. Cell size is about function, specific types of cells are usually the same size, how exactly do organisms manage them so precisely?
To understand what this is all about, let’s talk about cell cycles first.
For a normal cell, it’s about two big things in its life: growing up and having cubs. The two things alternate, one can be called a cell cycle.
Looking at the graph, this ring is a more intuitive embodiment of the cell cycle. During the filament (M) period, the cells complete the birth of a child in two, and at other times (intertempor), the cells slowly grow to prepare for division. Phase S is the time when cell DNA replicates, while G1/G2 cells grow up.
As for the G0, that’s the cell “the world is so big I want to see” self-relaxation time.
In mammalian cells, the point in time for this transition from growth to cubs occurs mainly in the transition from G1 to S. Although scientists have found that changes in cell cycle regulatory factors affect cell size, it’s not clear exactly how exactly it will change the life planning of cells.
Past research has found some of the answers. One of the mechanisms that regulate the size and life cycle of cells is to change the concentration of a particular signaling molecule. For example, in germinated yeast, there is a cell cycle-suppressing protein Whi5, which dilutes the concentration of Whi5 in the cell during the G1 cell length conference, triggering the cell cycle.
In mammalian cells, there are also proteins that function like Whi5, namely Rb, p107, and p130, members of the retinoblastoma protein family. They can advance the cell cycle by binding and suppressing E2F transcription factors.
Previous studies have found that the lack of Rb in mouse cells changes cell size, so is Rb the Whi5 for human cells?
First you have to see the Rb in the cell. The researchers attached the Rb protein to the green fluorescent protein so that the number of Rbs could be measured. From the experimental results, the amount of Rb protein in the G1 period basically unchanged, and subsequently increased in the S/G2/M period, while the nucleus volume of Rb presence also increased steadily.
Changes in the number of Rb proteins in the cell cycle.
In contrast, another similarly functioning cell cycle suppresses the protein p21, which begins to accumulate in The G1 and then rapidly degrades as it enters Phase S.
The researchers tested four different human cells and found that the number of Rbs had little to do with the size of the cells.
As for Rb’s two other relatives, the level of p107 was basically stable, while p130 was not expressed in the cell cycle.
From this point of view, Rb is the diluted cell cycle switch.
The researchers changed the expression of Rb in cells by changing the number of Rb alleles, and the results were interesting. The researchers found that the concentration of Rb had a very large effect on the cell cycle, and that every 2.5 times the Difference in The Rb concentration resulted in a frequent difference of 10 hours in G1 – normally the entire cell cycle would often be 16-17 hours;
In addition, there is an interesting discovery in the experiment.
When cells are split in two, they are not always equal, but the researchers found that whether the two separate dissoced cells are the same size or a small size, they are actually about the same. The researchers believe this may be the binding relationship between Rb and the chromosome, which is commonly divided into two sub-cells as chromosomes are separated.
It can be seen that when cells divide, the action of Rb and chromosomeis is basically synchronized.
It’s quite like a family property.