Faculty Bibliography

Aminoacyl-tRNAs (aa-tRNAs) are delivered to the ribosome as part of the ternary complex of aa-tRNA, elongation factor Tu (EF-Tu) and GTP. Here, we present a cryo-electron microscopy (cryo-EM) study, at a resolution of approximately 9 A, showing that during the incorporation of the aa-tRNA into the 70S ribosome of Escherichia coli, the flexibility of aa-tRNA allows the initial codon recognition and its accommodation into the ribosomal A site. In addition, a conformational change observed in the GTPase-associated center (GAC) of the ribosomal 50S subunit may provide the mechanism by which the ribosome promotes a relative movement of the aa-tRNA with respect to EF-Tu. This relative rearrangement seems to facilitate codon recognition by the incoming aa-tRNA, and to provide the codon-anticodon recognition-dependent signal for the GTPase activity of EF-Tu. From these new findings we propose a mechanism that can explain the sequence of events during the decoding of mRNA on the ribosome

PAR proteins distribute asymmetrically across the anterior-posterior axis of the 1-cell-stage C. elegans embryo, and function to establish subsequent anterior-posterior asymmetries. By the end of the 4-cell stage, anteriorly localized PAR proteins, such as PAR-3 and PAR-6, redistribute to the outer, apical surfaces of cells, whereas posteriorly localized PAR proteins, such as PAR-1 and PAR-2, redistribute to the inner, basolateral surfaces. Because PAR proteins are provided maternally, distinguishing apicobasal from earlier anterior-posterior functions requires a method that selectively prevents PAR activity after the 1-cell stage. In the present study we generated hybrid PAR proteins that are targeted for degradation after the 1-cell stage. Embryos containing the hybrid PAR proteins had normal anterior-posterior polarity, but showed defects in apicobasal asymmetries associated with gastrulation. Ectopic separations appeared between lateral surfaces of cells that are normally tightly adherent, cells that ingress during gastrulation failed to accumulate nonmuscle myosin at their apical surfaces and ingression was slowed. Thus, PAR proteins function in both apicobasal and anterior-posterior asymmetry during the first few cell cycles of embryogenesis

Single cell PCR studies showed that hematopoietic stem cells (HSCs) express a variety of lineage-affiliated genes. However, it remains unclear whether these cells exhibiting 'lineage priming' represent bona fide stem cells or a subpopulation earmarked for differentiation. Here we have used a Cre-Lox approach to follow the fate of cells expressing a lineage-affiliated marker. We crossed lysozyme Cre mice with yellow fluorescent protein (EYFP) reporter mice and found EYFP gene expression not only in myelomonocytic cells but also in a fraction of HSCs as well as B cells and T cells. Transplantation of EYFP+ HSCs into primary and secondary recipients generated mice in which all hematopoietic cells were EYFP+. In contrast, crosses between CD19 Cre and lck Cre mice with reporter mice showed no EYFP expression in HSCs or intermediate progenitors. Our results demonstrate that lysozyme expression does not mark myeloid commitment and that long-term repopulation potential is maintained in primed HSCs

Epithelial stem cells play a central role in tissue homeostasis, wound repair, and carcinogenesis. Corneal epithelial stem cells have been demonstrated to reside in the limbal epithelium, while the fornical zone of the conjunctiva appears to be a predominant site of conjunctival epithelial stem cells. Stem cells of the corneal and conjunctival epithelia, as well as the hair follicle and interfollicular epidermis share important features: they are capable of self renewal; they are relatively quiescent (slow-cycling); they can be induced to proliferate; and they are multipotent. Its becoming apparent that a certain degree of flexibility exists between corneal and hair follicle keratinocytes

5-FU has been a key chemotherapeutic agent in the treatment of advanced or recurrent gastric cancer. In order to enhance the effect of 5-FU, biochemical modulation or combined chemotherapy has been developed. Although several phase III studies have been reported in 1990's, a standard chemotherapeutic regimen has not been established worldwide. Recently, newly developed anticancer agents such as CPT-11, TS-1, Paclitaxel, or Docetaxel can be clinically used for advanced gastric cancer either single agent or in combination that may further improve the quality of life and prolong the survival of patients with gastric cancer. In Japan, postoperative adjuvant chemotherapy has been actively developed to enhance survival benefit of surgery for patients with gastric cancer. There were a few positive single randomized controlled study showing benefit of adjuvant chemotherapy with a high evidence level. However, all reports of meta-analysis of adjuvant chemotherapy for gastric cancer indicated the survival benefit of adjuvant chemotherapy. At present, a nation-wide randomized controlled study in the postoperative adjuvant setting for gastric cancer using TS-1 (ACTS-GC) is under way that may clarify the effect of postoperative adjuvant chemotherapy in gastric cancer.

We report the first class II transposon in cephalochordates, which we have named Amphioxus Transposable Element 1 (ATE-1). ATE-1 members have been identified in the genome of Branchiostoma lanceolatum (BlATE-1) and B. floridae (BfATE-1). Structural analysis revealed that ATE-1 elements consist of a central region (CR) with no homology with any coding sequence, nor any detectable open reading frame (ORF), flanked by internal direct repeats (DR) of about 100 nt, each adjacent to a terminal inverted repeat (TIR) of 16 nt. Although the estimated copy number in the amphioxus genome is low, there is evidence of mobility. Sequence and hybridization analyses pointed to TIR and DR inter-species conservation, whereas no structural similarities among the CR were detected. Moreover, this element is found in two amphioxus species that diverged long ago, which argues in favor of its ancient origin. However, the structural hallmarks needed for transposition are still preserved.

The mammalian central nervous system (CNS) contains a remarkable array of neural cells, each with a complex pattern of connections that together generate perceptions and higher brain functions. Here we describe a large-scale screen to create an atlas of CNS gene expression at the cellular level, and to provide a library of verified bacterial artificial chromosome (BAC) vectors and transgenic mouse lines that offer experimental access to CNS regions, cell classes and pathways. We illustrate the use of this atlas to derive novel insights into gene function in neural cells, and into principal steps of CNS development. The atlas, library of BAC vectors and BAC transgenic mice generated in this screen provide a rich resource that allows a broad array of investigations not previously available to the neuroscience community