Re-creating an RNA world.

The RNA world hypothesis states that life originated via a system based on RNA genomes and RNA catalysts. Researchers have been trying to develop such a system since catalytic RNAs (ribozymes) were discovered in 1982. This review summarizes the recent progress made in that endeavor and outlines the obstacles that remain to be overcome. After giving a short background on prebiotic chemistry and in vitro evolution, the discussion focuses on the generation of three important components of an RNA world: a sufficient polymerase ribozyme, self-replicating membrane compartments and ribozymes that are capable of performing basic metabolic processes.

Annealing of RNA editing substrates facilitated by guide RNA-binding protein gBP21.

RNA editing within the mitochondria of African trypanosomes is characterized by the insertion and deletion of uridylate residues into otherwise incomplete primary transcripts. The reaction takes place in a high molecular mass ribonucleoprotein (RNP) complex of uncertain composition. Furthermore, factors that interact with the RNP complex during the reaction are by and large unknown. Here we present evidence for an editing-related biochemical activity of the gRNA-binding protein gBP21. Using recombinant gBP21 preparations, we show that the protein stimulates the annealing of gRNAs to cognate pre-mRNAs in vitro. This represents the presumed first step of the editing reaction. Kinetic data establish an enhancement of the second order rate constant for the gRNA- pre-mRNA interaction. gBP21-mediated annealing is not exclusive for RNA editing substrates since complementary RNAs, unrelated to the editing process, can also be hybridized. The gBP21-dependent RNA annealing activity was identified in mitochondrial extracts of trypanosomes and can be inhibited by immunoprecipitation of the polypeptide. The data suggest a factor-like contribution of gBP21 to the RNA editing process by accelerating the rate of gRNA-pre-mRNA anchor formation.

The involvement of gRNA-binding protein gBP21 in RNA editing-an in vitro and in vivo analysis.

RNA editing in the parasitic organism Trypanosoma brucei is characterised by the insertion and deletion of uridylate residues into otherwise incomplete primary transcripts. The processing reaction is a required pathway for the expression of most mitochondrial genes and proceeds by a cascade of enzyme-catalysed steps. RNA editing involves one or more macromolecular ribonucleoprotein complexes which are likely to interact with additional components as the reaction proceeds. Here we examined the involvement of the gRNA-binding polypeptide gBP21, a protein which has been demonstrated to be associated with active RNA editing complexes. We show that in vitro RNA editing can be suppressed by the addition of a gBP21-specific antibody or by immunodepletion of the protein. By creating a gBP21 knockout mutant we analysed the requirement for the protein in vivo. gBP21(-) trypanosomes are viable as bloodstream stage cells and contain edited mRNAs. However, the knockout mutant is not capable of differentiating from the bloodstream to the insect life cycle stage in vitro. Moreover, mutant cells are characterised by a low mitochondrial transcript abundance. Together, these data establish that gBP21 contributes a non-essential function to the RNA editing reaction and further suggest that the protein is involved in additional mitochondrial processes which impact a larger pool of mitochondrial transcripts.

Trypanosoma brucei gBP21. An arginine-rich mitochondrial protein that binds to guide RNA with high affinity.

RNA editing in Trypanosoma brucei is a mitochondrial RNA processing reaction that results in the insertion and deletion of uridylate residues into otherwise untranslatable mRNAs. The process is directed by guide RNAs which function to specify the edited sequence. RNA editing in vitro requires mitochondrial protein extracts and guide RNAs have been identified as part of high molecular weight ribonucleoprotein complexes. Within the complexes, the RNAs are in close contact with several mitochondrial proteins and here we describe the isolation and cloning of a gRNA-interacting polypeptide from Trypanosoma brucei. The protein was named gBP21 for guide RNA-binding protein of 21 kDa. gBP21 shows no homology to proteins in other organisms, it is arginine-rich and binds to gRNA molecules with a dissociation constant in the nanomolar range. The protein does not discriminate for differences in the primary structures of gRNAs and thus likely binds to higher order structural features common to all gRNA molecules. gBP21 binding does not perturb the overall structure of gRNAs but the gRNA/gBP21 ribonucleoprotein complex is more stable than naked guide RNAs. Although the protein is arginine-rich, the free amino acid or an arginine-rich peptide were not able to inhibit the association to the RNAs. In contrast, the gRNA-gBP21 complex formation was sensitive to potassium and ammonium cations, thus indicating a contribution of ionic contacts to the binding.

Moving places: a glance at the Gulf War from the sealed room.

During the recent Gulf War a mental health team was set up to deal with immediate stress reactions and to help prevent future difficulties in a group of a few hundred temporarily relocated evacuees from a working- and lower-class suburb of Tel Aviv, Israel. The contextually specific acute stress reaction syndrome observed in the affected population is described. A conceptualization was formulated which served the staff to deal with the problems that arose during this period. Concepts such as potential space, stranger anxiety, environment mother, triangulation in families in conflict, disruption of continuity, and holding and containing were integrated in order to illuminate some aspects of the stressful situation and to deal with problems that arose. The reactions of the mental health professionals to the situation and the relationships of the team with the evacuees and with their colleagues are discussed.

Object relations, Holocaust survival and family therapy.

The authors focus on a family therapy, construing the process of change within an object-relations theory integrated with psychodynamic thoughts about Holocaust survivors. Specifically, the authors concentrate on the mutual influence of parents and their children as figures for a two-way identification, and on the potential constructive role the offspring may have in promoting change, in this case reparative change, in the family. A clinical illustration of such a family treated by one of the authors illustrates this aspect. The disturbed intra-familial relationships in the history of each parent led to the development of pathological internalized object relations. This was reinforced by traumatic life-events, especially with the father who was a Holocaust survivor. Serious problems developed in marital life and in relation with the children. Couple therapy alone did not seem successful. The couple who lived in a sado-masochistic collusion for years could not change. Only after including the children in the therapy did the family's relations improve. Confrontation with some positive aspects of the family which the children represent may have been a factor in this change. The couple were able to resynthesize and integrate positive aspects of themselves as represented and reinforced by their children. It seems that reparation through the children helped modify all relations in the family.