Question

QUESTION 21

1. Describe the function of FOS in normal cells and cancer cells.

   For a complete answer, you will need to include:

   A) its mechanism of action, including other proteins it works with and its downstream targets

   B) how its activity is regulated

   C) whether it acts as an oncogene or a tumor suppressor and why inactivation or activation of the gene leads to cancer

   QUESTION 22

2. Signal Transduction:

   A) Explain how growth factors, acting through the signal transduction pathway, regulate cell proliferation.  Names of specific proteins and their function must be given.

   B) Give 2 specific examples of how an alteration in the signal transduction pathway can lead to cancer

QUESTION 23

1. Cell Cycle Regulation:

   Describe the mechanism by which the cell cycle is regulated by mitogens. In your answer, be sure to include the following:

   a) The phases of the cell cycle and protein whose concentrations vary during the cell cycle

   b) The complexes formed by the proteins in (a) and the mechanisms by which they are regulated

   c) The substrate of the complexes in (b) and its role in cell cycle control

   d) Describe 2 ways in which the substrate in (c) can be inactivated to cause cancer

QUESTION 24

1. DNA Damage and the cell cycle:

   Describe the mechanism by which DNA damage such as a double-strand break leads to cell cycle arrest.

   Be sure to include:

   a) how the pathway is regulated

   b) why it is important to regulate the cell cycle during conditions of DNA damage

Answer 1

FOS is a protooncogenewhich encode 62 KDa protien and form activation of protien complex.It binds to DNA at the AP-1 specific siteat the promoter and enhancer region of the target gene and changes the expression of gene. It has found to be overexpressed in cancer and can also perform normal cellular function and is called immediate early gene.In normal cells it helps in cellular proliferation, differentiation and survival.Hypoxia and angiogenesis genes are regulatedleads to cancer development.It can cause the loss of cellular polarity and epithelial mesenchymal transition leads to metastatic growth in mammary epithelial cells.Over expression of FOS from Class I MHC leads to formation of osteosarcoma by increased prolifertaion of osteoclasts.cFOS has tumour supressor activity. In ovarian carcinomal cells loss of cFOS expression leads to dosease progression.cFOS is a mediator of c-myc - induced cell death and induce apoptosis with p38MAP kinase pathway.Influence direct regulation of BRCA-! and suppress tumour.Apoptopic mechanism is found in T-Cell leukemia.

It can be used as indirect marker in neuronal activity.Amylin response neurons in the AP can promote neuraxis and peripheral stimulation.Used in drug abuse research.C fos - Cjun regulate cell death by apoptosis.

2.Ligands binds to cell surface receptor and takes new shape and bind other molecule. Receptor turn on other signal molecule inside the cell and activate its own target..G1 Phase is controlled by PRB protiens and response activity of E2F transcription which promote mitosis.Phosphorylation of PRB protiens by G1 cyclin dependent kinas e release CDK inhibitor.Mitogenis and anti proliferative signal effect cell proliferation by transcriptional regulation and ubiquitin dependent degradation of cyclin and CDK inhibitors. Growth factors that stimulate , growth differentation, survival and tissue repair . Fibroblast growth factor,Vascular endothelial , endodermal, Epidermal and platelet induced , Insulin like and transformin growth factors. It activate receptors results in activation of other protiens in signal pathway and produce second messenger and induce specific genes.Cancer causing mutation effect the signal pathways and leads to cancer and dysregulation of celluar process by oncogenic genes.

Please post the remaining questions as another set, then I will be able to answer it.