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

http://www.klinikaikozpont.u-szeged.hu/pedia/images/pdf/CME_TEL/Full-Text/25.pdf

The Hallmarks of Aging

Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

Aggregation-Induced Emission: Together We Shine, United We Soar!

The terminus of a DNA helix has been called its Achilles' heel. Thus to prevent possible incomplete replication and instability of the termini of linear DNA, eukaryotic chromosomes end in characteristic repetitive DNA sequences within specialized structures called telomeres. In immortal cells, loss of telomeric DNA due to degradation or incomplete replication is apparently balanced by telomere elongation, which may involve de novo synthesis of additional repeats by novel DNA polymerase called telomerase. Such a polymerase has been recently detected in HeLa cells. It has been proposed that the finite doubling capacity of normal mammalian cells is due to a loss of telomeric DNA and eventual deletion of essential sequences. In yeast, the est1 mutation causes gradual loss of telomeric DNA and eventual cell death mimicking senescence in higher eukaryotic cells. Here, we show that the amount and length of telomeric DNA in human fibroblasts does in fact decrease as a function of serial passage during ageing in vitro and possibly in vivo. It is not known whether this loss of DNA has a causal role in senescence.

Telomeres shorten during ageing of human fibroblasts.

BIOE 402. Medical Technology Assessment. 2 or 3 hours. Bioentrepreneur course. Assessment of medical technology in the context of commercialization. Objectives, competition, market share, funding, pricing, manufacturing, growth, and intellectual property; many issues unique to biomedical products. Course Information: 2 undergraduate hours. 3 graduate hours. Prerequisite(s): Junior standing or above and consent of the instructor.

“Bioinformatics” 특집을 내면서

Subpopulations of RNA molecules that bind specifically to a variety of organic dyes have been isolated from a population of random sequence RNA molecules. Roughly one in 10(10) random sequence RNA molecules folds in such a way as to create a specific binding site for small ligands.

In vitro selection of RNA molecules that bind specific ligands.

https://www.cell.com/cell/pdf/0092-8674(83)90331-8.pdf

The double-strand-break repair model for recombination

Covalent fusions between an mRNA and the peptide or protein that it encodes can be generated by in vitro translation of synthetic mRNAs that carry puromycin, a peptidyl acceptor antibiotic, at their 3′ end. The stable linkage between the informational (nucleic acid) and functional (peptide) domains of the resulting joint molecules allows a specific mRNA to be enriched from a complex mixture of mRNAs based on the properties of its encoded peptide. Fusions between a synthetic mRNA and its encoded myc epitope peptide have been enriched from a pool of random sequence mRNA-peptide fusions by immunoprecipitation. Covalent RNA-peptide fusions should provide an additional route to the in vitro selection and directed evolution of proteins.

/pdf/rna-peptide-fusions-for-the-in-vitro-selection-of-peptides-11ve88ti01.pdf

RNA-peptide fusions for the in vitro selection of peptides and proteins

DNA molecules that integrate into yeast chromosomes during yeast transformation do so by homologous recombination We have studied the way in which circular and linear molecules recombine with homologous chromosomal sequences We show that DNA ends are highly recombinogenic and interact directly with homologous sequences Circular hybrid plasmids can integrate by a single reciprocal crossover, but only at a low frequency Restriction enzyme digestion within a region homologous to yeast chromosomal DNA greatly enhances the efficiency of integration Furthermore, if two restriction cuts are made within the same homologous sequence, thereby removing an internal segment of DNA, the resulting deleted-linear molecules are still able to transform at a high frequency Surprisingly, the integration of these gapped-linear molecules results in replacement of the missing segment using chromosomal information The final structure is identical to that obtained from integration of a circular molecule The integration of linear and gapped-linear molecules, but not of circular molecules, is blocked by the rad52-1 mutation Consideration of models for plasmid integration and gene conversion suggests that RAD52 may be involved in the DNA repair synthesis required for these processes Implications of this work for the isolation of integrative transformants, fine-structure mapping, and the cloning of mutations are discussed

https://www.pnas.org/content/pnas/78/10/6354.full.pdf

Yeast transformation: a model system for the study of recombination

In vitro selection allows rare functional RNA or DNA molecules to be isolated from pools of over 10(15) different sequences. This approach has been used to identify RNA and DNA ligands for numerous small molecules, and recent three-dimensional structure solutions have revealed the basis for ligand recognition in several cases. By selecting high-affinity and -specificity nucleic acid ligands for proteins, promising new therapeutic and diagnostic reagents have been identified. Selection experiments have also been carried out to identify ribozymes that catalyze a variety of chemical transformations, including RNA cleavage, ligation, and synthesis, as well as alkylation and acyl-transfer reactions and N-glycosidic and peptide bond formation. The existence of such RNA enzymes supports the notion that ribozymes could have directed a primitive metabolism before the evolution of protein synthesis. New in vitro protein selection techniques should allow for a direct comparison of the frequency of ligand binding and catalytic structures in pools of random sequence polynucleotides versus polypeptides.

/pdf/in-vitro-selection-of-functional-nucleic-acids-2gyp6kaqym.pdf

Jack W. Szostak

Papers

In vitro selection of RNA molecules that bind specific ligands.

The double-strand-break repair model for recombination

RNA-peptide fusions for the in vitro selection of peptides and proteins

Yeast transformation: a model system for the study of recombination

In vitro selection of functional nucleic acids.