抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

The HER-2/neu oncogene is a member of the erbB-like oncogene family, and is related to, but distinct from, the epidermal growth factor receptor. This gene has been shown to be amplified in human breast cancer cell lines. In the current study, alterations of the gene in 189 primary human breast cancers were investigated. HER-2/neu was found to be amplified from 2- to greater than 20-fold in 30% of the tumors. Correlation of gene amplification with several disease parameters was evaluated. Amplification of the HER-2/neu gene was a significant predictor of both overall survival and time to relapse in patients with breast cancer. It retained its significance even when adjustments were made for other known prognostic factors. Moreover, HER-2/neu amplification had greater prognostic value than most currently used prognostic factors, including hormonal-receptor status, in lymph node-positive disease. These data indicate that this gene may play a role in the biologic behavior and/or pathogenesis of human breast cancer.

https://science.sciencemag.org/content/sci/235/4785/177.full.pdf

Human breast cancer: correlation of relapse and survival with amplification of the HER-2/neu oncogene

Through the study of transcriptional activation in response to interferon alpha (IFN-alpha) and interferon gamma (IFN-gamma), a previously unrecognized direct signal transduction pathway to the nucleus has been uncovered: IFN-receptor interaction at the cell surface leads to the activation of kinases of the Jak family that then phosphorylate substrate proteins called STATs (signal transducers and activators of transcription). The phosphorylated STAT proteins move to the nucleus, bind specific DNA elements, and direct transcription. Recognition of the molecules involved in the IFN-alpha and IFN-gamma pathway has led to discoveries that a number of STAT family members exist and that other polypeptide ligands also use the Jak-STAT molecules in signal transduction.

https://science.sciencemag.org/content/sci/264/5164/1415.full.pdf

Jak-STAT pathways and transcriptional activation in response to IFNs and other extracellular signaling proteins

Apoptosis plays an important role during neuronal development, and defects in apoptosis may underlie various neurodegenerative disorders. To characterize molecular mechanisms that regulate neuronal apoptosis, the contributions to cell death of mitogen-activated protein (MAP) kinase family members, including ERK (extracellular signal-regulated kinase), JNK (c-JUN NH2-terminal protein kinase), and p38, were examined after withdrawal of nerve growth factor (NGF) from rat PC-12 pheochromocytoma cells. NGF withdrawal led to sustained activation of the JNK and p38 enzymes and inhibition of ERKs. The effects of dominant-interfering or constitutively activated forms of various components of the JNK-p38 and ERK signaling pathways demonstrated that activation of JNK and p38 and concurrent inhibition of ERK are critical for induction of apoptosis in these cells. Therefore, the dynamic balance between growth factor-activated ERK and stress-activated JNK-p38 pathways may be important in determining whether a cell survives or undergoes apoptosis.

https://science.sciencemag.org/content/sci/270/5240/1326.full.pdf

Opposing Effects of ERK and JNK-p38 MAP Kinases on Apoptosis

Protein kinase C, an enzyme that is activated by the receptor-mediated hydrolysis of inositol phospholipids, relays information in the form of a variety of extracellular signals across the membrane to regulate many Ca2+-dependent processes. At an early phase of cellular responses, the enzyme appears to have a dual effect, providing positive forward as well as negative feedback controls over various steps of its own and other signaling pathways, such as the receptors that are coupled to inositol phospholipid hydrolysis and those of some growth factors. In biological systems, a positive signal is frequently followed by immediate negative feedback regulation. Such a novel role of this protein kinase system seems to give a logical basis for clarifying the biochemical mechanism of signal transduction, and to add a new dimension essential to our understanding of cell-to-cell communication.

https://science.sciencemag.org/content/sci/233/4761/305.full.pdf

Studies and perspectives of protein kinase C

Transcription of the c-fos proto-oncogene is greatly increased within minutes of administering purified growth factors to quiescent 3T3 cells. This stimulation is the most rapid transcriptional response to peptide growth factors yet described, and implies a role for c-fos in cell-cycle control. Transformation by c-fos may result from a temporal deregulation of this control.

Stimulation of 3T3 cells induces transcription of the c- fos proto-oncogene

Nerve growth factor and epidermal growth factor induce rapid transient changes in proto-oncogene transcription in PC12 cells.

Cholinergic agonists rapidly and transiently induced transcription of the c-fos protooncogene and one or more actin genes in neuronally differentiated PC12 cells. Transcription was activated within minutes after stimulation of the nicotinic acetylcholine receptor and required an influx of extracellular Ca2+ ions through voltage-sensitive calcium channels. Nicotine activation proceeded by a different pathway from activation by nerve growth factor, whose stimulation of these genes is independent of extracellular Ca2+ ions. These findings suggest that neurotransmitters may rapidly activate specific gene transcription in nondividing neuronally differentiated cells. They also suggest a functional role for neurotransmitter induction of c-fos and actin expression in the nervous system.

https://science.sciencemag.org/content/sci/234/4772/80.full.pdf

Stimulation of neuronal acetylcholine receptors induces rapid gene transcription

Mutagenesis of the fos protein supports the hypothesis that a heptad repeat of leucine residues stabilizes the interaction between the fos and jun proteins. We show that the complex between fos and jun can bind to DNA more tightly than either protein alone and that basic residues adjacent to the leucine repeat offos contribute to the DNA-binding potential of the complex.

The role of the leucine zipper in the fos–jun interaction

The three-dimensional structure of the basic/helix–loop–helix/leucine zipper domain of the transcription factor Max complexed with DNA has been determined by X-ray crystallography at 2.9 A resolution. Max binds as a dimer to its recognition sequence CACGTG by direct contacts between the α-helical basic region and the major groove. This symmetric homodimer, a new protein fold, is a parallel, left-handed, four-helix bundle, with each monomer containing two α-helical segments separated by a loop. The two α-helical segments are composed of the basic region plus helix 1 and helix 2 plus the leucine repeat, respectively. As in GCN4, the leucine repeat forms a parallel coiled coil.

Edward B. Ziff

Papers

Stimulation of 3T3 cells induces transcription of the c- fos proto-oncogene

Nerve growth factor and epidermal growth factor induce rapid transient changes in proto-oncogene transcription in PC12 cells.

Stimulation of neuronal acetylcholine receptors induces rapid gene transcription

The role of the leucine zipper in the fos–jun interaction

Recognition by Max of its cognate DNA through a dimeric b/HLH/Z domain.