Question

n cancer cells, chromatin around proto-oncogenes and tumor suppressors is often changed in comparison to cells that are not cancerous. Considering that higher expression of proto-oncogenes and lower expression of tumor suppressors (in comparison to normal cells) could lead to a cancerous phenotype, would you expect that the following changes/differences in chromatin in cells could lead to a cancerous phenotype?

"Higher levels of HATs around proto-oncogenes"

Answer 1

Answer: The genes are capable of causing cancer are called oncogenes. Once means tumour or mass.

Activation of proto-oncogenes to oncogenes-

There are many mechanisms

1) viral insertion into chromosome:

When certain retroviruses infectcells, a complimentary DNA is made form their RNA by the enzyme reverse transcriptase. The cena so produced get inserted into the host genome. Activation of protooncogene myc to oncogene by viral insertion ultimately causing carcinogens.some DNA viruses also get inserted into the host cell chromosome and activat the protooncogenes.

e.g. Avian leukaemia.

2) chromosomal translocation:

This is due to the rearrangement of genetic material (DNA) by chromosomal translocation. It usually results in over expression of protooncogenes.

3)Gene amplification:

Several fold amplification of certain DNA sequences are observed in some cancers . It is associated with administration of anticancer drugs methotrexate . Amplification results in increase in activity of dihydrofolate reductase.

4) point mutation:

The Ras protooncogene is the best example of activation by point mutation. The mutated ras oncogenes produces a GTPase protein which differs in structure by a single amino acid. This alteration diminishes the activity of GTPase, cakey enzyme involving in control of cell growth.

Mechanism of action of oncogenes = oncogenes encodes for certain proteins namely oncoproteins. It depends on

a) Growth factors

b)cell proliferation

C) growth factor receptor (TGFalpha)

d) GTP binding protein.

Tumors makers:

The biochemical indicator employed to detect the presence of cancers are collectively referred to to the tumour makers. These are the abnormally produced molecules of tumor cells such as surface antigens, cyoplasmic proteins, enzymes and hormones. Tumor makers can be measured in serum.

A couple of the most commonly used tumors makes or suppressor are carcinoembryonic antigen(CEA)and alpha fetoprotein(AFP) .

Metastasis is a important aspect of growing tumor cells. It refers to the spread of cancer cells from the primary site of origin to the other tissues of the body where they get deposited and secondary tumors.

Biochemical changes like increase replication and transcription, increase glycolysis ,synthesis of fetal proteins have major roles.