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Research round-up

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Sharing transcription duties

By | June 13, 2000

The transcription factors TFIID and SAGA are multi-subunit complexes involved in RNA polymerase II transcription. In the 8 June Nature Lee et al. use oligonucleotide arrays to analyze the relative requirement for the two complexes in yeast (Nature 2000, 405:701-704). Expression of about 70% of yeast genes requires one or more of the subunits shared between TFIID and SAGA, although individual subunits were required to varying extents, and no single subunit was required to the same extent as RNA p

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The birth of AIDS

By | June 13, 2000

According to a new phylogenetic analysis, the subtype of HIV that causes the majority of AIDS cases started diverging around 1931. The results of the analysis, which was conducted on the Los Alamos supercomputer 'Nirvana' using sequences from 159 envelope genes, are reported in the 9 June Science (Korber et al., Science 2000, 288:1789-1796). The computation used a molecular clock model presuming a constant rate of sequence change, but similar results were obtained with models that allowed change

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A lot of bloody genes

By | June 7, 2000

In the 2 June Science, Phillips et al announce the creation of the Stem Cell Database (SCDb), an annotated collection of genes expressed in hematopoietic stem cells (Science 2000, 288:1635-1640). Most of the data are based on the sequencing of 5735 clones from a subtracted stem cell library, representing at least half of the library's complexity. The SCDb reveals clues to stem cell biology, such as the coincidence of semaphorins and their ligands, suggesting that these molecules are important fo

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Gene, regulate thyself

By | June 7, 2000

The stochastic nature of every chemical event in the cell generates noise that can lead to large fluctuations in protein and mRNA levels. Autoregulatory negative feedback loops in gene circuits have been proposed, but never shown, to be one way of limiting this variation. With a simple experiment, in the 1 June Nature Becskei and Serrano demonstrate that negative feedback can decrease the inherent variability of gene expression more than threefold. They direct expression of a hybrid protein (gre

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Stem cells branch out

By | June 7, 2000

Differentiation of embryonic stem (ES) cells, which are originally totipotent, puts increasing restrictions on the final fates that a cell can achieve. This simple idea was upset last year when neural stem cells were shown to produce blood cells in irradiated adult mice. In the 2 June issue of Science, Clarke et al. show that neural stem cells injected into embryos can generate a wide variety of tissues including cells in the central nervous system, heart, liver, and intestine (Science 2000, 288

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Microbead expression arrays

By | June 6, 2000

Strategies for expression analysis range from exhaustive sequencing (and thus counting) of cDNAs to hybridization arrays. In the June issue of Nature Biotechnology Brenner et al. describe a method that combines the digital precision of the former with the speed and throughput of the latter (Nat. Biotech. 2000, 18:630-634). Brenner et al. attach tagged cDNAs to microbeads and then sequence the overhanging ends of the cDNAs by detecting the hybridization of fluorescently labeled probes. After one

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