The stem cell protein Lin28 functions to inhibit the biogenesis of a group of miRNAs but also stimulates the expression of a subset of mRNAs at the post-transcriptional level, the underlying mechanism of which is not yet understood. Here we report the characterization of the molecular interplay between Lin28 and RNA helicase A (RHA) known to play an important role in remodeling ribonucleoprotein particles during translation. We show that reducing Lin28 expression results in decreased RHA association with polysomes while increasing Lin28 expression leads to elevated RHA association. Further, the carboxyl terminus of Lin28 is necessary for interaction with both the amino and carboxyl termini of RHA. Importantly, a carboxyl terminal deletion mutant of Lin28 that retains RNA-binding activity fails to interact with RHA and exhibits dominant-negative effects on Lin28-dependent stimulation of translation. Taken together, these results lead us to suggest that Lin28 may stimulate translation by actively recruiting RHA to polysomes.
Loss-of-function studies in human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) via nonviral approaches have been largely unsuccessful. Here we report a simple and cost-effective method for high-efficiency delivery of plasmids and siRNAs into hESCs and iPSCs. Using this method for siRNA delivery, we achieve >90% reduction in the expression of the stem cell factors Oct4 and Lin28, and observe cell morphological and staining pattern changes, characteristics of hESC differentiation, as a result of Oct4 knockdown.
Summary A number of Rho-kinase inhibitors have been developed for various clinical applications. We examined the effects of the Rho-kinase inhibitor Y27632 on keratinocyte proliferation and migration, and found it promoted primary human keratinocyte proliferation and migration in both monolayer and skin explant cultures. In addition, topical application of Y27632 enhanced cutaneous wound closure in the majority of wounds in mice. The growth and migration effects of Y27632 appeared to be specific to keratinocytes compared with dermal fibroblasts, and required intact Jun kinase function. Y27632 seems to be a promising agent for keratinocyte procurement and wounding healing. A number of pharmacological inhibitors of the Rho signalling cascade have been developed for biological and clinical applications. One of these, Y27632, an inhibitor of Rho-associated protein kinase (ROCK),1,2 has been shown to increase embryonic stem-cell survival and keratinocyte stem-cell procurement in culture.3–6 The aim of this study was to examine how Y27632 affects keratinocyte and dermal fibroblast cell growth and migration, and to evaluate the in vivo effects of this reagent on cutaneous wound healing.
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