Augustine Yonghwi Kim

Global identification of target recognition and cleavage by the Microprocessor in human ES cells

The Microprocessor plays an essential role in canonical miRNA biogenesis by facilitating cleavage of stem-loop structures in primary transcripts to yield pre-miRNAs. Although miRNA biogenesis has been extensively studied through biochemical and molecular genetic approaches, it has yet to be addressed to what extent the current miRNA biogenesis models hold true in intact cells. To address the issues of in vivo recognition and cleavage by the Microprocessor, we investigate RNAs that are associated with DGCR8 and Drosha by using immunoprecipitation coupled with next-generation sequencing. Here, we present global protein–RNA interactions with unprecedented sensitivity and specificity. Our data indicate that precursors of canonical miRNAs and miRNA-like hairpins are the major substrates of the Microprocessor. As a result of specific enrichment of nascent cleavage products, we are able to pinpoint the Microprocessor-mediated cleavage sites per se at single-nucleotide resolution. Unexpectedly, a 2-nt 3′ overhang invariably exists at the ends of cleaved bases instead of nascent pre-miRNAs. Besides canonical miRNA precursors, we find that two novel miRNA-like structures embedded in mRNAs are cleaved to yield pre-miRNA-like hairpins, uncoupled from miRNA maturation. Our data provide a framework for in vivo Microprocessor-mediated cleavage and a foundation for experimental and computational studies on miRNA biogenesis in living cells.

Bioproduction of mushroom mycelium of Agaricus bisporus by commercial submerged fermentation for the production of meat analogue

BACKGROUND As worldwide interest in healthy and delicious meat analogues increases, the texture of these products has become an important indicator of quality. Mycoprotein as fungal mycelium could provide a distinctive chewing sensation; however, the unfavorable consumer perception of fungal mycelium demands the production of meat analogues with true mushroom mycelium. RESULTS The industrial and economical bioprocess was developed using an inexpensive medium (30 g L(-1) sugar cane extract (SCE), 10 g L(-1) NaNO(3) and 5 g L(-1) yeast extract) and A. bisporus Suksung. The SCE was maintained at around 10 g L(-1) to minimize osmotic shock. The maximum mycelium production of 15.0 g L(-1) (dry weight) was reached within 4 days. Scanning electron microscopic analysis showed fibrous and directional structure rather than a more typical pellet structure. Meat analogues with mushroom mycelium had better textural properties, being higher in hardness, springiness, and chewiness and with preferable umami characteristics compared to meat analogues utilizing soy protein. The overall acceptance of meat analogues prepared with mycelium and soy protein, and a ground beef patty, were 5, 2 and 10, respectively. CONCLUSION The development of an industrial bioprocess for A. bisporus mycelium allowed the production of a highly acceptable meat analogue having not only superior textural properties but also umami characteristics when compared to that of soy protein.

Identification of novel stress-induced microRNAs and their targets in Camelina sativa using computational approach

MicroRNAs (miRNAs) are a class of small non-coding, single-stranded RNA sequences that regulate gene expression at the post-transcriptional level and also reported to function in stress responses, but their role has not been studied in Camelina (Camelina sativa L.), an emerging oil crop. In this study, we predicted conserved as well as putative novel miRNAs from a Camelina drought stress cDNA library using comprehensive genomic approaches. Based on the sequence homology, we predicted 145 miRNAs, of which 61 were conserved, and 84 putative novel miRNAs were found to belong to 26 and 72 different miRNA families, respectively. In silico expression analysis indicated that 20 miRNAs were really expressed in Camelina genome, and several of them have tissue-specific expression character. We found that the 60 putative novel miRNA families target 117 genes. Most of the miRNA targets were predicted to genes including that regulate stress response, transcription factors, and fatty acid and lipid metabolism-related genes. Expression patterns of 6 randomly selected miRNAs under drought stress were validated by real-time quantitative polymerase chain reaction analysis. Coordinated expression changes between 6 randomly selected miRNAs and their target genes, suggested that the predicted miRNAs could be drought-responsive and that they would likely be directly involved in stress regulatory networks of Camelina. These results indicate that, in C. sativa, under drought stress, a large number of new miRNAs could be discovered, and the predicted stress-responsive miRNAs and their target transcripts will serve as valuable resources for future studies.

Complete genome sequence of Stenotrophomonas sp. KCTC 12332, a biotechnological potential bacterium

Hydroxy fatty acids are used in various industries due to their availability, and in particular, Stenotrophomonas sp. has been regarded as a potential candidate for biotechnological applications, including biotransformation that hydrate unsaturated fatty acids into their derivatives. Here we complete the genome sequence of Stenotrophomonas sp. KCTC 12332 which has a size of 4,541,594bp (G+C content of 63.83%) with 3790 coding DNA sequences (CDSs), 67 tRNA and 3 rRNA operons. The genome contains gene encoding oleate hydratase that can convert oleic acid into 10-hydroxyoctadecanoic acid.

Complete genome sequence of the xylan-degrading Mucilaginibacter sp. strain PAMC26640 isolated from an Arctic lichen

Mucilaginibacter sp. PAMC26640 is a xylan-degrading bacterium isolated from the Arctic lichen Stereocaulon sp. Here, we present the first complete genome sequence of Mucilaginibacter sp. strain PAMC26640, which contains several genes involved in xylan utilization. This genome information provides new insights into the genetic basis of its physiology and further analysis of key metabolic genes related to the xylan degradation pathway.

Complete genome sequence of Hymenobacter sp. strain PAMC26554, an ionizing radiation-resistant bacterium isolated from an Antarctic lichen

A Gram-negative, rod-shaped, red-pink in color, and UV radiation-resistant bacterium Hymenobacter sp. strain PAMC26554 was isolated from Usnea sp., an Antarctic lichen, and belongs to the class of Cytophagia and the phylum of Bacteroidetes. The complete genome of Hymenobacter sp. PAMC26554 consists of one chromosome (5,244,843bp) with two plasmids (199,990bp and 6421bp). The genomic sequence indicates that Hymenobacter sp. strain PAMC26554 possesses several genes involved in the nucleotide excision repair pathway that protects damaged DNA. This complete genome information will help us to understand its adaptation and novel survival strategy in the Antarctic extreme cold environment.

Crystallization and preliminary X-ray crystallographic analysis of free methionine-(R)-sulfoxide reductase from Staphylococcus aureus

Free methionine-(R)-sulfoxide reductase (fRMsr) catalyzes the reduction of the free form of methionine-(R)-sulfoxide back to free methionine. The fRMsr protein from Staphylococcus aureus was overexpressed in Escherichia coli, purified and crystallized at 295 K using ammonium sulfate as a precipitant. Diffraction data were collected to 1.7 angstrom resolution from a native crystal using synchrotron radiation. The crystal belonged to the hexagonal space group P6(1)22, with unit-cell parameters a = b = 89.84, c = 88.75 angstrom, alpha = beta = 90, gamma = 120 degrees. Assuming the presence of one molecule in the asymmetric unit, the calculated Matthews coefficient value was 2.21 angstrom(3) Da(-1), with a solvent content of 57.1%.