Hey Salman

Thanks for your question.

This is right up my alley, as my research is based on how FGF-10 (Fibroblast Growth Factor) influences transcription factors in the developing lung! First let’s talk about transcription factors vs. growth factors, and to what those two phrases refer. Transcription factors are proteins that bind to DNA (directly, or sometimes indirectly) to encourage transcription of a particular gene or genes. Growth factors are (typically secreted) molecules that interact with other molecules (receptors) to influence cellular behavior, both through transcription and other molecular messengers.

Let’s talk about lung for example. In the lung a growth factor, FGF-10, is secreted by one population of cells to encourage the budding and branching of the airways. FGF-10 does not possess the ability to bind with DNA and encourage any cellular behaviors by directly influencing transcription. Instead it interacts with its receptor (the Fibroblast Growth Factor Receptor 2) on the surface of the cells in the airway. When it interacts with the receptor, the receptor phosphorylates itself. This phosphorylation event leads to other downstream proteins also being phosphorylated. This cascade of phosphorylation can directly affect the cell cycle and lead to increased (or even decreased) cell division (mitosis). It can also lead to activation of transcription factors that affect cell growth and division. These particular transcription factors like c-Jun an c-Fos, which are crucial for the changes required for proper lung development, are also proto-oncogenes. They work by upregulating transcription of genes required for these behaviors. They are also commonly mutated and improperly activated in cancers.

Some growth factors and their receptors are considered proto-oncogenes, for instance one of the Epidermal Growth Factor receptors (Her2) is an oncogene that is strongly upregulated in many breast cancers. In fact, some forms of breast cancer have responded well to drugs that specifically block Her2. There are many examples of growth factors and their receptors running amok and leading to cancerous growths. The estrogen receptor is a little tricky, as different mutations can make it behave like either a tumor suppressor or an oncogene. Some breast cancers depend on estrogen to continue to grow, while others stop growing when faced with estrogen. I could not find any sources that specifically named estrogen or the estrogen receptor proto-oncogenes.

In your question you mention that “transcription factors affected the transcription of target genes and decide which proteins to make and when” and that growth factors “affect the RATE of transcription and cell division.” Well, those are both true statements. But transcription factors can also affect cell division by upregulating the expression of genes that lead to cell division or cell senescence (preventing cell division). Similarly, while growth factors often change the rate of transcription and cell division, they also affect other cellular functions such as cell survival, cell growth, cell motility and cell shape. Most cellular processes that require growth factors also require transcription factors downstream of those growth factors to mediate cellular processes.

I’m not sure what you mean by “second messenger model.” There are molecules that act as messengers between growth factors and the processes they regulate, just as transcription factors are also typically regulated by other molecules.

I hope this helps you out! This is such a complicated topic I could write many pages about the behavior of transcription factors and growth factors!

Billy.

PS – I’ve included a few links I think might be helpful for your studies.  

Her2 Positive Breast Cancer.

http://www.mayoclinic.com/health/breast- cancer/an00495

From Mayo Clinic’s website.  A good practical demonstration of how an oncogene can directly influence cancer virulence. 

Oncogenes and Tumor Supressors.

http://www.cancer.org/docroot/eto/content/eto_1_4x_ oncogenes_and_tumor_suppressor_genes.asp

A good introduction to oncogenes and tumor suppressors and how each figure into carcinogenesis.  

Human Epidermal Growth Factor Receptor (HER) Signaling.

http://www.bi ooncology.com/bioonc/research/her/index.m

This is a neat site that talks specifically about Epidermal Growth Factor signaling.  I think the video very strongly illustrates the connection between growth factor signaling and transcription factors (in this case the endpoint being MAPK in the video).  

Transcription Factors (by AIT-SI- ALI)

http://atlasgeneticsoncology.org/Deep/TranscripFactorsID20043.html

This is an excellent review of transcription factors and the specific families of transcription factors that are currently known.  I suggest you take a look at the paragraphs on Myc and p53.  

Cell Signaling

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellSignaling.html

This is a great overview of cell signaling (including growth factors) that you might find helpful…it is maintained by John Kimball, an immunologist at Harvard.