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Paramyxoviruses are thought to edit their P gene mRNAs co‐transcriptionally, by a mechanism in which the polymerase stutters and reads the same template base more than once. Sendai virus (SeV) and bovine parainfluenza virus type 3 (bPIV3) are closely related viruses, but SeV edits its P gene mRNA with the insertion of a single G residue (at approximately 50% frequency) within the sequence 5′ A6G3, whereas bPIV3 inserts 1 to approximately 6 Gs at roughly equal frequency within the sequence 5′ A6G4. When SeV synthetic mini‐genomes containing either SeV or bPIV3 P gene editing cassettes are expressed from cDNA in cells which are also transfected with the SeV NP, P and L genes, the virus‐specific editing patterns were reproduced. Since the bPIV3 editing pattern was reproduced in a system that is otherwise completely SeV, this suggests that all the information for the virus‐specific editing patterns is due to the RNA sequence itself. Unexpectedly, the length of the template C run was found to be critical, even though it varies from 3 to 7 nucleotides in length in different viruses. Expanding this template C run first led to attenuation of the insertion phenotype, and then to deletions rather than insertions. A stuttering or slippage model to account for these events has been further refined to include a pressure which displaces the nascent strand in a given direction once it has disengaged from the template, and the similarities of this model to those which account for readthrough of cellular RNA polymerase transcription blocks are discussed.

A G--~ T mutation at the start-point of transcription of the phage P22 sat promoter (sor+ 1T) causes a novel defect in promoter clearance by Escherichia coli RNA polymerase (RNAP) in vitro. Under standard transcription conditions, in the presence of high concentrations of all four NTPs, the predominant products from this promoter are poly(U) chains of varying length. Because the mutation creates a run of four T : A base-pairs from -1 to + 3 (TGTT --, TTTT), we propose that synthesis of poly(U) is pseudo-templated by the A4 stretch on the template strand. G --* A and G --* C mutations at position + 1 do not cause pseudo-templated transcription. Several molecules of poly(U) are produced and released per sar+ IT promoter-polymerase complex without dissociation of RNAP from the template DNA. The exponential relationship between yield and size of individual poly(U) species indicates that there is a constant probability that another U residue will be added to the nascent chain. Presumably, pseudo-templated transcription occurs by a slippage (stuttering) mechanism like that proposed to explain certain kinds of RNA editing in eukaryotic viral mRNAs.[Key Words: E. coli RNA polymerase; pseudo-templated transcription; Sar + 1 T]Received May 11, 1990; revised version accepted July 31, 1990.Initiation of transcription by E. coli RNA polymerase (RNAP) is a complex process that can be divided into several steps: (1) initial binding of the polymerase holoenzyme (core enzyme + cr) to form an unstable "closed" complex; (2) isomerization to form a stable "open" complex in which the DNA around the start point of transcription is unwound; (3) initiation of RNA synthesis; and (4) promoter clearance, which includes release of the promoter and (r subunit, and formation of a stable ternary complex of DNA, nascent RNA, and core enzyme.Much attention has focused on the early steps leading to formation of the open complex because the rate of open complex formation is clearly a primary determinant of promoter strength and is often the target of control by repressors and activators (for review, see Hoopes andYager and von Hippel 1987). Footprinting studies of open complexes on several different promoters show that the polymerase is in close proximity to the promoter DNA between about -50 and +20 and that the region from -9 to +3 is unwound. Within the protected region are the two stretches of DNA sequence that are most highly conserved among promoters, the -35 and -10 regions. The importance of these sequences is underscored by analyses of promoter-down and promoter-up mutations, most of which cluster in the conserved hexamers 5'-ICoztesponding author.

Natural antisense RNAs have stem-loop (hairpin) secondary structures that are important for their function. The sar antisense RNA of phage P22 is unusual: the 3' half of the molecule forms an extensive stem-loop, but potential structures for the 5' half are not predicted to be thermodynamically stable. We devised a novel method to determine the secondary structure of sar RNA by examining the electrophoretic mobility on non-denaturing gels of numerous sar mutants. The results show that the wild-type RNA forms a 5' stem-loop that enhances electrophoretic mobility. All mutations that disrupt the stem of this hairpin decrease mobility of the RNA. In contrast, mutations that change the sequence of the stem without disrupting it (e.g. change G.U to A.U) do not affect mobility. Nearly all mutations in single-stranded regions of the structure also have no effect on mobility. Confirmation of the proposed 5' stem-loop was obtained by constructing and analyzing compensatory double mutants. Combinations of mutations that restore a base-pair of the stem also restore mobility. The genetic phenotypes of sar mutants confirm that the proposed secondary structure is correct and is essential for optimal activity of the antisense RNA in vivo.

Quebec, a province in Canada, is well positioned in the global bioeconomy. Its regions are overflowing with forest, agricultural crops or other organic residues that can be recovered and converted into bioproducts and bioenergy. Quebec's strength has long been in the forest products industry and municipal solid waste recycling. Product diversification is now targeted by many companies and municipalities. Value chains for bioproducts and bioenergy are set in practically all of Quebec's regions. In fact, most of them have their own ''communityscale'' bioeconomy project, even if the province of Quebec itself does not have yet its own bioproducts or bioeconomy roadmap. In this paper, various community-scale bioeconomy projects are presented and discussed. The role of cities and other local stakeholders in the deployment of these projects and the focus on getting products or coproducts for local uses are also elaborated. A framework involving the positive involvement of national and regional institutions and the development of a network with local stakeholders is proposed to increase the chance of success of community-scale bioeconomy projects. Community-Scale Bioeconomy Case Studies in Quebec Community-scale bioeconomy refers to activities related to the development of bioresources production and processing supported actively by local private and public stakeholders in a