MicroRNAs: Genomics, Biogenesis, Mechanism, and Function

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://bartellab.wi.mit.edu/publication_reprints/Bartel_Cell09.pdf

MicroRNAs: Target Recognition and Regulatory Functions

We have mapped and quantified mouse transcriptomes by deeply sequencing them and recording how frequently each gene is represented in the sequence sample (RNA-Seq). This provides a digital measure of the presence and prevalence of transcripts from known and previously unknown genes. We report reference measurements composed of 41–52 million mapped 25-base-pair reads for poly(A)-selected RNA from adult mouse brain, liver and skeletal muscle tissues. We used RNA standards to quantify transcript prevalence and to test the linear range of transcript detection, which spanned five orders of magnitude. Although >90% of uniquely mapped reads fell within known exons, the remaining data suggest new and revised gene models, including changed or additional promoters, exons and 3′ untranscribed regions, as well as new candidate microRNA precursors. RNA splice events, which are not readily measured by standard gene expression microarray or serial analysis of gene expression methods, were detected directly by mapping splice-crossing sequence reads. We observed 1.45 × 10 5 distinct splices, and alternative splices were prominent, with 3,500 different genes expressing one or more alternate internal splices. The mRNA population specifies a cell’s identity and helps to govern its present and future activities. This has made transcriptome analysis a general phenotyping method, with expression microarrays of many kinds in routine use. Here we explore the possibility that transcriptome analysis, transcript discovery and transcript refinement can be done effectively in large and complex mammalian genomes by ultra-high-throughput sequencing. Expression microarrays are currently the most widely used methodology for transcriptome analysis, although some limitations persist. These include hybridization and cross-hybridization artifacts 1–3 , dye-based detection issues and design constraints that preclude or seriously limit the detection of RNA splice patterns and previously unmapped genes. These issues have made it difficult for standard array designs to provide full sequence comprehensiveness (coverage of all possible genes, including unknown ones, in large genomes) or transcriptome comprehensiveness (reliable detection of all RNAs of all prevalence classes, including the least abundant ones that are physiologically relevant). Other

/pdf/mapping-and-quantifying-mammalian-transcriptomes-by-rna-seq-1egh5oivst.pdf

Mapping and quantifying mammalian transcriptomes by RNA-Seq.

https://www.um.es/biomybiotec/web/Seminarios/2010/papers/Cano_2.pdf

Epithelial-Mesenchymal Transitions in Development and Disease

Evolutionary bioscience as regulatory systems biology

SpHmx,a Sea Urchin Homeobox Gene Expressed in Embryonic Pigment Cells

Measurements are reported of the thermal stability of DNA heteroduplexes between clones of the eta-globin pseudogene from a variety of primates. The known sequences of this 7.1-kb region differ from each over a range from 1.6% for human versus chimp to nearly 12% for human versus spider monkey. Thermal stability was determined by standard hydroxyapatite thermal elution, and the results show a precisely linear decrease in thermal stability with divergence. The slope of the regression line is 1.18% sequence divergence per degree centigrade reduction in thermal stability.

Calculation of sequence divergence from the thermal stability of DNA heteroduplexes.

Exclusive developmental functions of gatae cis-regulatory modules in the Strongylocentrorus purpuratus embryo

The CyIIIa actin gene of Strongylocentrotus purpuratus is transcribed exclusively in the embryonic aboral ectoderm, under the control of 2.3 kb cis-regulatory domain that contains a proximal module that controls expression in early embryogenesis, and a middle module that controls expression in later embryogenesis. Previous studies demonstrated that the SpRunt-1 target site within the middle module is required for the sharp increase in CyIIIa transcription which accompanies differentiation of the aboral ectoderm, and that a negative regulatory region near the SpRunt-1 target site is required to prevent ectopic transcription in the oral ectoderm and skeletogenic mesenchyme. This negative regulatory region contains a consensus binding site for the myb family of transcription factors. In vitro DNA-binding experiments reveal that a protein in blastula-stage nuclei interacts specifically with the myb target site. Gene transfer experiments utilizing CyIIIa reporter constructs containing oligonucleotide substitutions indicate that this site is both necessary and sufficient to prevent ectopic expression of CyIIIa. Synthetic oligonucleotides containing the myb target site were used to purify a protein from sea urchin embryo nuclear extracts by affinity chromatography. This protein is immunoprecipitated by antibodies specific to the evolutionarily conserved myb domain, and amino acid sequences obtained from the purified protein were found to be identical to sequences within the myb domain. Sequence information was used to obtain cDNA clones of SpMyb, the S. purpuratus member of the myb family of transcription factors. Through interactions within the middle module, SpMyb functions to repress activation of CyIIIa in the oral ectoderm and skeletogenic mesenchyme.

/pdf/spmyb-functions-as-an-intramodular-repressor-to-regulate-26g0hdcqzr.pdf

Eric H. Davidson

Papers

Evolutionary bioscience as regulatory systems biology

SpHmx,a Sea Urchin Homeobox Gene Expressed in Embryonic Pigment Cells

Calculation of sequence divergence from the thermal stability of DNA heteroduplexes.

Exclusive developmental functions of gatae cis-regulatory modules in the Strongylocentrorus purpuratus embryo

SpMyb functions as an intramodular repressor to regulate spatial expression of CyIIIa in sea urchin embryos