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Affymetrix/Cold Spring Harbor Laboratory ENCODE Transcriptome Project * The repertoire of RNAs found in eukaryotic cells is unexpectedly complex, with virtually the entire non-repeat portions of many genomes being transcribed [...], The transcriptomes of eukaryotic cells are incredibly complex. Individual non-coding RNAs dwarf the number of protein-coding genes, and include classes that are well understood as well as classes for which the nature, extent and functional roles are obscure (1). Deep sequencing of small RNAs (

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2006.06.009 Byline: Aarron T. Willingham (1), Thomas R. Gingeras (1) Abstract: The widespread occurrence of noncoding (nc) RNAs -- unannotated eukaryotic transcripts with reduced protein coding potential -- suggests that they are functionally important. Study of ncRNAs is increasing our understanding of the organization and regulation of genomes. Author Affiliation: (1) Affymetrix, Inc., Santa Clara, CA 95051, USA

Endogenous and exogenous short interfering RNAs (siRNAs) require a 5'-phosphate for loading into Ago2 and cleavage of the target mRNA. We applied a synthetic 5'-phosphate to siRNA guide strands to evaluate if phosphorylation in vivo is rate limiting for maximal siRNA knockdown and duration. We report, for the first time, an in vivo evaluation of siRNAs with a synthetic 5'-phosphate compared to their unphosphorylated versions. siRNAs that contained a 5'-phosphate had the same activity in vivo compared with unphosphorylated siRNAs, indicating phosphorylation of an siRNA is not a rate limiting step in vivo. [ABSTRACT FROM AUTHOR]

Recent evidence of genome-wide transcription in several species indicates that the amount of transcription that occurs cannot be entirely accounted for by current sets of genome-wide annotations. Evidence indicates that most of both strands of the human genome might be transcribed, implying extensive overlap of transcriptional units and regulatory elements. These observations suggest that genomic architecture is not colinear, but is instead interleaved and modular, and that the same genomic sequences are multifunctional: that is, used for multiple independently regulated transcripts and as regulatory regions. What are the implications and consequences of such an interleaved genomic architecture in terms of increased information content, transcriptional complexity, evolution and disease states? [ABSTRACT FROM AUTHOR]

miRNAs are ∼22-nt RNAs that bind to the Argonaute family of proteins and have important regulatory roles in plants and animals. Here, we show that miRNAs exhibit targeting activity in cells when delivered as single strands that are 5'-phosphorylated and that contain 2'-fluoro ribose modifications. Length preferences, chemical modification sensitivity, and genome-wide seed-based targeting all suggest that this activity is Ago-based. Activity could be enhanced by annealing of segmented passenger strands containing non-nucleic acid spacers. Furthermore, screening of randomly generated sequences identified pyrimidine rich 3' cassette sequences that increased single strand activity. These results provide an initial step in the development of single-stranded miRNA mimics for therapeutic use.