Final answer:
The first biochemical activity for oncogenes discovered was the enzyme-linked tyrosine kinase activity of the EGF receptor, leading to the award of the 1986 Nobel Prize to Rita Levi-Montalcini. This discovery has been pivotal in understanding how signals for cell proliferation are transmitted and has led to advancements in cancer biology and treatment.
Step-by-step explanation:
The Discovery of the Biochemical Activity of Oncogenes
The first biochemical activity of oncogenes to be discovered was linked to the EGF receptor, which is an enzyme-linked tyrosine kinase. This significant discovery laid the groundwork for our understanding of how signals for cell proliferation are transmitted within cells. Rita Levi-Montalcini won the 1986 Nobel Prize in Physiology or Medicine for discovering the EGF receptor along with the mechanism of receptor kinase signal transduction. When effector ligands bind to monomer membrane receptor kinases, they dimerize, and SH₂ proteins that contain sulfhydryl groups then bind to each monomer. The kinase domain of the receptor becomes activated, cross-phosphorylations occur, and the SH₂ proteins disengage—allowing the receptors to interact with other cytoplasmic proteins to continue the signal transduction pathway, often leading to cellular proliferation.
It was later found that oncogenes were initially discovered in viruses but were also present as mutations in cell genes, as demonstrated when J. Michael Bishop and Harold Varmus received the 1964 Nobel Prize for showing that the src (sarcoma) gene of the Rous Sarcoma Virus originated from cells. Oncogenes are essentially mutated versions of normal genes involved in cell growth and division, and when these genes are activated in an uncontrolled manner, they can lead to the transformation of normal cells into cancerous ones.
Understanding the function of oncogenes has greatly contributed to cancer biology; for instance, HER2 is a receptor that, when overexpressed due to gene duplication, contributes to 20 to 25 percent of human breast cancers. HER2 overexpression led to the development of Herceptin (trastuzumab), a targeted therapy that has improved the overall survival rate of patients with metastatic breast cancer.
Overall, oncogenes can function as hormones, growth factors, and are integral to the signaling pathways that control cell growth and division. Mutations in oncogenes can disrupt the normal regulation of the cell cycle, leading to uncontrolled cell growth and the development of tumors.