Lin28 inhibits the expression of let-7 microRNAs but also exhibits let-7-independent functions. Using immunoprecipitation and deep sequencing, we show here that Lin28 preferentially associates with a small subset of cellular mRNAs. Of particular interest are those for ribosomal proteins and metabolic enzymes, the expression levels of which are known to be coupled to cell growth and survival. Polysome profiling and reporter analyses suggest that Lin28 stimulates the translation of many or most of these targets. Moreover, Lin28-responsive elements were found within the coding regions of all target genes tested. Finally, a mutant Lin28 that still binds RNA but fails to interact with RNA helicase A (RHA), acts as a dominantnegative inhibitor of Lin28-dependent stimulation of translation. We suggest that Lin28, working in concert with RHA, enhances the translation of genes important for the growth and survival of human embryonic stem cells. STEM CELLS 2011;29:496-504 Disclosure of potential conflicts of interest is found at the end of this article.

Residual dipolar coupling (RDC), a robust anisotropic NMR parameter for structural elucidation of organic molecules, is only accessible in an anisotropic environment. Herein, we introduce a novel alignment medium based on the molecular self‐assembly of oligopeptide amphiphile (OPA). This medium is compatible with different intermediate and polar solvent systems, such as CD3OD, [D6]DMSO, and D2O. The preparation of the OPA‐based medium is simple and rapid, while only very weak background signals were observed from OPAs. Furthermore, we show that the purity of OPA has only a minor influence on the quality of the RDC data. These advantages allow RDC measurements of organic molecules with different polarities and solubilities with high efficiency and accuracy.

Residual dipolar couplings (RDCs) have proven to be an invaluable anisotropic NMR parameter for the structural elucidation of complex biopolymers and organic molecules. However, a remaining bottleneck limiting its wider use by organic and natural product chemists is the lack of a range of easily applicable aligning media for diverse organic solvents. In this study, graphene oxide (GO) liquid crystals (LCs) were developed to induce partial orientation of organic molecules to allow RDC measurements. These LCs were determined to be maintainable at very low concentrations (as low as 1 mg/ mL, corresponding to quadrupolar 2 H splittings ranging from 2.8 to 30 Hz and maximum 13 C− 1 H dipolar couplings of 20 Hz for camphor in a CH 3 COCH 3 /water system) and to be remarkably stable and broadly compatible with aqueous and organic solvents such as dimethyl sulfoxide, CH 3 COCH 3 , and CH 3 CN. Moreover, compared with those for other alignment media, very clean and high-quality NMR spectra were acquired with the GO molecules in solution because of their rigidity and high molecular weight. The developed medium offers a versatile and robust method for RDC measurements that may routinize the RDC-based structure determination of organic molecules. have been widely used to determine the 3D structures of biopolymers and organic molecules. Among these parameters, RDCs can reflect long-range structural restraints of global character and thus have been demonstrated to improve the precision and accuracy of NMR structures of biomolecules and to provide deeper insight into their internal dynamics. 4 In the past few years, RDC-enhanced structure analysis for organic molecules has attracted increasing attention because it allows the determination of the relative configuration of organic molecules in addition to constitution and conformation.