Our findings reveal a new regulatory pathway of YY1/HDACs/miR-155/HBP1 in macrophage-derived foam cell formation during early atherogenesis and suggest that miR-155 is a potential therapeutic target for atherosclerosis.
MicroRNAs are endogenous small RNA molecules that regulate gene expression. Although the biogenesis of microRNAs and their regulation have been thoroughly elucidated, the degradation of microRNAs has not been fully understood. Here by using the pulse–chase approach, we performed the direct measurement of microRNA lifespan. Five representative microRNAs demonstrated a general feature of relatively long lifespan. However, the decay dynamic varies considerably between these individual microRNAs. Mutation analysis of miR-29b sequence revealed that uracils at nucleotide position 9–11 are required for its rapid decay, in that both specific nucleotides and their position are critical. The effect of uracil-rich element on miR-29b decay dynamic occurs in duplex but not in single strand RNA. Moreover, analysis of published data on microRNA expression profile during development reveals that a substantial subset of microRNAs with the uracil-rich sequence tends to be down-regulated compared to those without the sequence. Among them, Northern blotting shows that miR-29c and fruit fly bantam possess a relatively rapid turnover rate. The effect of uracil-rich sequence on microRNA turnover depends on the sequence context. The present work indicates that microRNAs contain sequence information in the middle region besides the sequence element at both ends.
A minimal linear gene cassette (35S-phytase gene-nos) with T-DNA borders was acquired by PCR and directly introduced into soybean through the pollen tube pathway. A total of 13% of T(1 )plants were positive for phyA by specific PCR. Southern blot analyses showed that phyA insertions were harbored stably in T(2) progeny. Phytase expression level increased 2.5-fold over a 6-week period; its highest activity was 150 U/mg protein, compared to 56 U/mg protein in untransformed controls. Activity of phytase increased to 125 FTU/kg in T(3) transgenic seeds as compared to 64 FTU/kg in wild-type plants.
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