Specificity of ARGONAUTE7-miR390 interaction and dual functionality in TAS3 trans-acting siRNA formation.

Trans-acting siRNA form through a refined RNAi mechanism in plants. miRNA-guided cleavage triggers entry of precursor transcripts into an RNA-DEPENDENT RNA POLYMERASE6 pathway, and sets the register for phased tasiRNA formation by DICER-LIKE4. Here, we show that miR390-ARGONAUTE7 complexes function in distinct cleavage or noncleavage modes at two target sites in TAS3a transcripts. The AGO7 cleavage, but not the noncleavage, function could be provided by AGO1, the dominant miRNA-associated AGO, but only when AGO1 was guided to a modified target site through an alternate miRNA. AGO7 was highly selective for interaction with miR390, and miR390 in turn was excluded from association with AGO1 due entirely to an incompatible 5' adenosine. Analysis of AGO1, AGO2, and AGO7 revealed a potent 5' nucleotide discrimination function for some, although not all, ARGONAUTEs. miR390 and AGO7, therefore, evolved as a highly specific miRNA guide/effector protein pair to function at two distinct tasiRNA biogenesis steps.

Insights into the multifactorial nature of preterm birth: proteomic profiling of the maternal serum glycoproteome and maternal serum peptidome among women in preterm labor.

OBJECTIVE: The purpose of this study was to identify peptide classifiers that predict spontaneous preterm birth (SPTB) among women in preterm labor (PTL) and to demonstrate specific protein pathways that are activated in PTL. STUDY DESIGN: Serum from 110 women with PTL between 20 weeks and 33 weeks 6 days of gestation was subjected to glycoprotein purification, matrix-assisted laser desorption ionization time-of-flight mass spectrometry peptide profiling, 2-dimensional liquid chromatography tandem mass spectrometry, and pathway analysis. Women were divided into 2 groups: delivery at <34 weeks' gestation (SPTB group) and delivery at > or =34 weeks' gestation (PTL group). RESULTS: Twenty-three peptide masses were identified that discriminated PTL from SPTB in 97% of cases. Fifty-two proteins were present differentially between PTL and SPTB; 48 of 52 proteins were classified into 1 of 4 functional pathways that were involved with PTL: (1) complement/coagulation cascade, (2) inflammation/immune response, (3) fetal-placental development, and (4) extracellular matrix proteins. CONCLUSION: Among women in PTL, proteomic analysis of serum peptides and glycoproteins classifies women who will deliver preterm and identifies specific protein pathways at work among individuals with "idiopathic" PTL.

Regulation of AUXIN RESPONSE FACTOR3 by TAS3 ta-siRNA affects developmental timing and patterning in Arabidopsis.

MicroRNAs (miRNAs) and trans-acting siRNAs (ta-siRNAs) in plants form through distinct pathways, although they function as negative regulators of mRNA targets by similar mechanisms . Three ta-siRNA gene families (TAS1, TAS2, and TAS3) are known in Arabidopsis thaliana. Biogenesis of TAS3 ta-siRNAs, which target mRNAs encoding several AUXIN RESPONSE FACTORs (including ARF3/ETTIN and ARF4 ) involves miR390-guided processing of primary transcripts, conversion of a precursor to dsRNA through RNA-DEPENDENT RNA POLYMERASE6 (RDR6) activity, and sequential DICER-LIKE4 (DCL4)-mediated cleavage events. We show that the juvenile-to-adult phase transition is normally suppressed by TAS3 ta-siRNAs, in an ARGONAUTE7-dependent manner, through negative regulation of ARF3 mRNA. Expression of a nontargeted ARF3 mutant (ARF3mut) in a wild-type background reproduced the phase-change phenotypes detected in rdr6-15 and dcl4-2 mutants, which lose all ta-siRNAs. Expression of either ARF3 or ARF3mut in rdr6-15 plants, in which both endogenous and transgenic copies of ARF3 were derepressed, resulted in further acceleration of phase change and severe morphological and patterning defects of leaves and floral organs. In light of the functions of ARF3 and ARF4 in organ asymmetry, these data reveal multiple roles for TAS3 ta-siRNA-mediated regulation of ARF genes in developmental timing and patterning.