Oncogenes in their proto-oncogene state
drive the cell cycle forward, allowing cells to proceed from one cell cycle stage to the next
. This highly regulated process becomes dysregulated due to activating genetic alterations that lead to cellular transformation.
Do proto-oncogenes stimulate the cell cycle?
Mutations in proto-oncogenes are typically dominant in nature, and the mutated version of a proto-oncogene is called an oncogene.
Often, proto-oncogenes encode proteins that function to stimulate cell division
, inhibit cell differentiation, and halt cell death.
What do the proto-oncogenes do?
Proto-oncogenes are a group of typical genes in a cell. They contain the necessary information for your body to make the proteins responsible for:
stimulating cell division, which makes cell growth possible
.
inhibiting cell differentiation, which is when cells change their function
.
How cellular proto-oncogenes regulate cell division and growth?
Proto-oncogene Function
Proto-oncogenes
encode intracellular regulatory proteins (e.g., protein kinases), growth factors, and growth factor receptors that occupy specific intracellular and cellular membrane sites
. All these are important for cell growth and differentiation.
What is proto-oncogene and tumor suppressor gene?
Proto-oncogenes and tumour suppressor genes are
two types of gene essential for the control of cell division
?
. When these genes are mutated the control of cell division is lost and a cell
?
can develop into a cancer. Proto-oncogenes are involved in driving cell division, like the accelerator in a car.
What are three mechanisms for converting a proto-oncogene to an oncogene?
Three genetic mechanisms activate oncogenes in human neoplasms:
(1) mutation, (2) gene amplification, and (3) chromosome rearrangements
. These mechanisms result in either an alteration of protooncogene structure or an increase in protooncogene expression (Figure 6-5).
How do mutations affect the cell cycle?
When one or more components of a cell cycle checkpoint are mutated,
the chances of genetic instability during one round of the cell cycle increase accordingly with consequent acceleration of cellular evolution from the normal to the cancerous state
.
When are CDK’s present inside the cell during the cell cycle?
When are cyclin-dependent kinases (CDKs) present inside the cell during the cell cycle? CDKs are
always present in the cell, but only become active when bound to other proteins called cyclins
.
Do proto-oncogenes stimulate?
Proto-oncogenes
stimulate cell growth
in a controlled manner that involves the interplay of a number of other genes. However, should a proto-oncogene become mutated in some way, it may become hyperactive, leading to uncontrolled cellular proliferation and the exaggeration of some normal cellular activities….
What type of protein that regulates the cell cycle is encoded by proto-oncogenes?
Proto-oncogenes encode
intracellular regulatory proteins
(e.g., protein kinases), growth factors, and growth factor receptors that occupy specific intracellular and cellular membrane sites. All these are important for cell growth and differentiation.
Are proto-oncogenes dominant or recessive?
Mutations in proto-oncogenes are usually acquired. Having a mutation in just 1 of the pair of a particular proto-oncogene is usually enough to cause a change in cell growth and the formation of a tumor. For this reason, oncogenes are said to be
dominant at the cellular level
.
Which of the following is an example of a proto-oncogene?
One example of a well known proto-oncogene is the
HER2 gene
. This gene codes for a transmembrane tyrosine kinase receptor called human epidermal growth factor receptor 2. This protein receptor is involved in the growth, repair and division of cells in the breast.
What happens when a cell loses control of the cell cycle?
When the cell cycle proceeds without control,
cells can divide without order and accumulate genetic errors that can lead to a cancerous tumor
.
What will be the result of uncontrolled cell division after repeated mutations in an oncogene?
Cancer
is the result of unchecked cell division caused by a breakdown of the mechanisms regulating the cell cycle. The loss of control begins with a change in the DNA sequence of a gene that codes for one of the regulatory molecules.
Which feature is the most important in regulation of the cell cycle?
Cyclins
are among the most important core cell cycle regulators.
What is P53’s role in the cell cycle?
It
controls several genes that play a role in the arrest of the cell cycle, cellular senescence, DNA repair system, and apoptosis
. P53 plays a crucial role in supporting DNA repair by arresting the cell cycle to purchase time for the repair system to restore genome stability.
What is the role of a tumor suppressor protein in a cell?
Tumor Suppressor Proteins
Control Cell Growth
Tumor suppressor proteins regulate orderly cell growth and differentiation by sensing the surrounding environment, transmitting signals to the nucleus, and directly affecting transcription, translation, survival, or cell division.
What is P53’s role in the cell cycle What does it specifically do?
P53 forms a homotetrameric transcription factor that is reported to
directly regulate ~500 target genes, thereby controlling a broad range of cellular processes, including cell cycle arrest, cell senescence, DNA repair, metabolic adaptation and cell death
.
What effect does methylation have on gene expression?
DNA methylation
regulates gene expression
by recruiting proteins involved in gene repression or by inhibiting the binding of transcription factor(s) to DNA.
What molecules regulate the expression of proto-oncogenes?
Proto-oncogenes encode intracellular regulatory proteins (e.g.,
protein kinases
), growth factors, and growth factor receptors that occupy specific intracellular and cellular membrane sites. All these are important for cell growth and differentiation.
What major disease is caused by cells growing and dividing out of control and what causes this to happen?
Cancer
is a disease caused when cells divide uncontrollably and spread into surrounding tissues. Cancer is caused by changes to DNA.
How is a proto-oncogene analogous to a gas pedal in the cell cycle?
The analogy of a car is often used to describe the function of proto-oncogenes, oncogenes and tumor suppressors in the cell cycle and cell division.
The gas pedal pushes the car/cell into the cell cycle and promotes cellular division
and the brake pedal stops the cell cycle and inhibits cellular division.
How do mutations affect gene expression?
Sometimes, gene variants (also known as mutations)
prevent one or more proteins from working properly
. By changing a gene’s instructions for making a protein, a variant can cause a protein to malfunction or to not be produced at all.
How do mutated suppressor genes affect the cell cycle?
When such genes are mutated,
the brake may be lifted, resulting in runaway cell growth known as cancer
. In contrast, oncogenes are genes that encode proteins involved in normal cell growth. When such genes are mutated, they may also cause cancer but they do so by activating the growth-promoting signals.
How do cyclins influence the process of cell division?
Cyclins. Cyclins are named such because they undergo a constant cycle of synthesis and degradation during cell division.
When cyclins are synthesized, they act as an activating protein and bind to Cdks forming a cyclin-Cdk complex
. This complex then acts as a signal to the cell to pass to the next cell cycle phase.
How does MPF regulate the cell cycle?
It stimulates the mitotic and meiotic phases of the cell cycle. MPF
promotes the entrance into mitosis (the M phase) from the G
2
phase by phosphorylating multiple proteins needed during mitosis
. MPF is activated at the end of G
2
by a phosphatase, which removes an inhibitory phosphate group added earlier.
