Stimulation of induction or inhibition of crown-gall tumor development by RNA-fragments U2. Interference by auxin]

RNA-fragments U2 obtained by mild degradation with RNase U2 of ribosomal RNA containing A and G nucleotides in excess are capable of exhibiting either a stimulatory effect on the induction of Crown-gall tumors or an inhibitory action on their subsequent development. These different effects are dependent on the moment at which RNA-fragments were introduced into wounded Pea seedlings infected by Agrobacterium tumefaciens B6. The results obtained in vitro and in vivo suggest that an interaction between auxin and RNA-fragments U2 may take place, either increasing the tumor induction or inhibiting the proliferation of tumourous cells.     

Secondary and topographic structure of ribosomal RNA 16S of Escherichia coli

We present a model for the secondary structure of 16S ribosomal RNA from E. coli. This model has been deduced by restricting the total number of theoretical base pairings using the following criteria: (1) susceptibility of residues towards enzymatic probes that are specific for either paired or single stranded regions; (2) reactivity of certain residues to chemical modification; (3) evidence for medium and long range interactions; (4) comparative analysis of ribosomal RNA sequences from other organisms.     

Ultrastructure of the particles reconstituted by complementation of extracts from chl-r mutants of Escherichia coli K 12]

By freeze-fracturing it is shown that the vesicles reconstituted by complementation of the chlA and chlB mutants of E. coli K 12 extracts are characterized by an asymmetric membrane bilayer. In a feature quite similar to the original intact plasma membranes, the membrane splits in two halves and the intramembranous particles are asymmetrically distributed on the two facture faces. It is proposed that the process of membrane reconstitution, which is also associated with the restoration of nitrate-reductase activity, relies on a sequence of increasing complexity of the molecular organisation.     

RNA fragments rich in G and A nucleotides obligatory for in vitro DNA replication of phages phi-X 174 and lambda]

Evidence was presented that in vitro conversion of single-stranded DNA of phage phi X 174 to the double-stranded replicative form by partially purified DNA-dependent DNA polymerase I requires a specific RNA fragment acting as primer (25-50 nucleotides). RNA fragments highly rich in nucleotides A and G were obtained by partial degradation of E. coli M 500 Sho-R ribosomal RNA with pancreatic ribonuclease. They become covalently bound to the newly synthesized DNA chain of the replicative form of phage phi X 174. These RNA fragments are also required for in vitro replication of lambda phage DNA.     

Cooperative non-specific binding of the cyclic adenosine 3'--5'-monophosphate receptor protein (CRP) from Escherichia coli to double-stranded thymus and lambda pgal DNA]

Either free or combined with cAMP, CRP binds cooperatively to double-stranded thymus and lambda pgal DNA. The affinity of CRP for both DNAs in these non-specific interactions is increased by cAMP without noticeable change in the degree of cooperativity. Values of the intrinsic association constant, cooperativity parameter, and site size of DNA were determined from ultracentrifugal investigations under near-physiological ionic conditions.     

Inhibition of in vitro RNA synthesis by hycanthone,oxamniquine and praziquantel

Summary The schistosomicides, hycanthone, oxamniquine and praziquantel, were found to inhibit the in vitro RNA synthesis using isolated hamster liver nuclei. Preincubation of the nuclei with these drugs revealed that the inhibitory effect of oxamniquine was irreversible and progressed with time, whereas that of hycanthone and parziquantel was reversible. On the other hand, hycanthone and praziquantel have a high affinity for DNA but oxamniquine does not. The data indicate that the mechanism of inhibition by oxamniquine is different from that of hycanthone and praziquantel.     

Inhibition of in vitro RNA synthesis by hycanthone, oxamniquine and praziquantel.

The schistosomicides, hycanthone, oxamniquine and praziquantel, were found to inhibit the in vitro RNA synthesis using isolated hamster liver nuclei. Preincubation of the nuclei with these drugs revealed that the inhibitory effect of oxamniquine was irreversible and progressed with time, whereas that of hycanthone and praziquantel was reversible. On the other hand, hycanthone and praziquantel have a high affinity for DNA but oxamniquine does not. The data indicate that the mechanism of inhibition by oxamniquine is different from that of hycanthone and praziquantel.     

The sigmaS subunit of RNA polymerase as a signal integrator and network master regulator in the general stress response in Escherichia coli

The sigmaS (RpoS) subunit of RNA polymerase in Escherichia coli is a key master regulator which allows this bacterial model organism and important pathogen to adapt to and survive environmentally rough times. While hardly present in rapidly growing cells, sigmaS strongly accumulates in response to many different stress conditions, partly replaces the vegetative sigma subunit in RNA polymerase and thereby reprograms this enzyme to transcribe sigmaS-dependent genes (up to 10% of the E. coli genes). In this review, we summarize the extremely complex regulation of sigmaS itself and multiple signal input at the level of this master regulator, we describe the way in which sigmaS specifically recognizes "stress" promoters despite their similarity to vegetative promoters, and, while being far from comprehensive, we give a short overview of the far-reaching physiological impact of sigmaS. With sigmaS being a central and multiple signal integrator and master regulator of hundreds of genes organized in regulatory cascades and sub-networks or regulatory modules, this system also represents a key model system for analyzing complex cellular information processing and a starting point for understanding the complete regulatory network of an entire cell.